Method for reporting channel state information on transmission opportunity duration in wireless access system supporting non-licensed band, and device supporting same

ABSTRACT

A method for transmitting channel state information (CSI) on a transmission opportunity (TxOP) duration by a user equipment (UE) in a wireless communication system supporting a unlicensed band, includes measuring CSI of the TxOP duration based on CSI interference measurement (CSI-IM) and/or CSI reference signal (CSI-RS) in one or more time intervals via the unlicensed band, wherein the one or more time intervals are determined based on a starting point of the TxOP duration; and transmitting the CSI to a base station.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.15/307,704 filed on Oct. 28, 2016, which was filed as the National Phaseof PCT International Application No. PCT/KR2015/004320, filed on Apr.29, 2015, which claims priority under 35 U.S.C. 119(e) to U.S.Provisional Application No. 61/986,087, filed on Apr. 29, 2014, all ofwhich are hereby expressly incorporated by reference into the presentapplication.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a wireless access system supporting anunlicensed band, and to a method for reporting channel state informationon a transmission opportunity duration and a device supporting the same.

DISCUSSION OF THE RELATED ART

Wireless access systems have been widely deployed to provide varioustypes of communication services such as voice or data. In general, awireless access system is a multiple access system that supportscommunication of multiple users by sharing available system resources (abandwidth, transmission power, etc.) among them. For example, multipleaccess systems include a Code Division Multiple Access (CDMA) system, aFrequency Division Multiple Access (FDMA) system, a Time DivisionMultiple Access (TDMA) system, an Orthogonal Frequency Division MultipleAccess (OFDMA) system, and a Single Carrier Frequency Division MultipleAccess (SC-FDMA) system.

SUMMARY OF THE INVENTION

The present invention relates to a wireless access system supporting anunlicensed band, and more particularly to a method for reporting channelstate information on a transmission opportunity (TxOP) duration and amethod supporting the same.

One object of the present invention is to provide a method forefficiently transmitting and receiving data in a wireless access systemsupporting an unlicensed band and a licensed band.

Another object of the present invention is to provide various methodsfor defining a transmission opportunity (TxOP) duration in an unlicensedband and configuring the TxOP duration.

Still another object of the present invention is to provide a method forconfiguring CSI-IM within a TxOP duration to measure channel stateinformation.

Further still another object of the present invention is to provide amethod for measuring interference by using CSI-IM and methods foraveraging interference.

Further still another object of the present invention is to providedevices for supporting the methods.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

The present invention relates to a wireless access system supporting anunlicensed band, and provides a method for reporting channel stateinformation on a transmission opportunity (TxOP) duration and devicesfor supporting the same.

In one aspect of the present invention, a method for reporting channelstate information (CSI) on a transmission opportunity (TxOP) duration ina wireless access system supporting carrier aggregation (CA) with anunlicensed band comprises the steps of receiving CSI interferencemeasurement (CSI-IM) configuration information related to the TxOPduration through a primary cell (Pcell); measuring interference atsubframes of a secondary cell (Scell), at which CSI-IM is configured, onthe basis of the CSI-IM configuration information; measuring CSI of theTxOP duration of the Scell by using the interference; and transmittingthe CSI to an eNB, wherein the Pcell is a serving cell configured in alicensed band, and the Scell is a serving cell configured in theunlicensed band.

At this time, the UE may measure the interference by using CSI-IM onlyincluded in the TxOP duration.

Otherwise, a period for configuring the CSI-IM may be configured to besmaller than a size of the TxOP duration, and the CSI-IM configurationinformation may include period information of the CSI-IM and sizeinformation of the TxOP duration.

Otherwise, the size of the TxOP duration and the period for configuringthe TxOP duration are configured based on period information of theCSI-IM, and the CSI-IM configuration information may include periodinformation P of the CSI-IM, period information K of the TxOP duration,and size information N of the TxOP duration.

At this time, the period information K may have a size of 2P, and thesize information N may be set to P+1.

The UE may measure interference on all CSI-IMs configured within aCSI-IM duration to perform interference averaging. At this time, theCSI-IM duration may be configured in a unit of one or more subframes orone or more TxOP durations. Also, the UE may perform interferenceaveraging by using only interference within a threshold value previouslyset based on a cumulative distribution function among interferencevalues measured based on the CSI-IM duration.

The method may further comprise the steps of calculating a firstinterference average value by using all interferences measured withinthe CSI-IM duration; and calculating a second interference average valueby using only interference less than the first interference averagevalue among all the interferences measured within the CSI-IM duration.

In another aspect of the present invention, a UE for reporting channelstate information (CSI) on a transmission opportunity (TxOP) duration ina wireless access system supporting carrier aggregation (CA) with anunlicensed band comprises a transmitter; a receiver; and a processor forcontrolling the transmitter and the receiver to report the CSI on theTxOP duration.

At this time, the processor may be configured to receive CSIinterference measurement (CSI-IM) configuration information related tothe TxOP duration through a primary cell (Pcell) by controlling thereceiver, measure interference at subframes of a secondary cell (Scell),at which CSI-IM is configured, on the basis of the CSI-IM configurationinformation, measure CSI of the TxOP duration of the Scell by using theinterference, and transmit the CSI to an eNB by controlling thetransmitter, and the Pcell may be a serving cell configured in alicensed band, and the Scell may be a serving cell configured in theunlicensed band.

At this time, the processor may measure the interference by using CSI-IMonly included in the TxOP duration.

Otherwise, a period for configuring the CSI-IM may be configured to besmaller than a size of the TxOP duration, and the CSI-IM configurationinformation may include period information of the CSI-IM and sizeinformation of the TxOP duration.

Otherwise, the size of the TxOP duration and the period for configuringthe TxOP duration may be configured based on period information of theCSI-IM, and the CSI-IM configuration information may include periodinformation P of the CSI-IM, period information K of the TxOP duration,and size information N of the TxOP duration. At this time, the periodinformation K may have a size of 2P, and the size information N may beset to P+1.

The processor may measure interference on all CSI-IMs configured withina CSI-IM duration to perform interference averaging. At this time, theCSI-IM duration may be configured in a unit of one or more subframes orone or more TxOP durations. Also, the processor may perform interferenceaveraging by using only interference within a threshold value previouslyset based on a cumulative distribution function among interferencevalues measured based on the CSI-IM duration.

The processor may further be configured to calculate a firstinterference average value by using all interferences measured withinthe CSI-IM duration and calculate a second interference average value byusing only interference less than the first interference average valueamong all the interferences measured within the CSI-IM duration.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

As is apparent from the above description, the embodiments of thepresent invention have the following effects.

First of all, data can efficiently be transmitted and received in awireless access system supporting an unlicensed band and a licensedband.

Secondly, methods for configuring CSI-IM within a TxOP duration can beprovided, whereby a UE can more exactly measure CSI on the TxOPduration.

Thirdly, methods for configuring a CSI-IM duration can be provided,whereby a UE can perform interference averaging. As a result, unexpectedinterference generated due to a hidden node problem can be removed.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the inventions. Thus, itis intended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention, illustrate embodiments of the inventionand together with the description serve to explain the principle of theinvention.

FIG. 1 is a conceptual diagram illustrating physical channels used inthe embodiments and a signal transmission method using the physicalchannels.

FIG. 2 is a diagram illustrating a structure of a radio frame for use inthe embodiments.

FIG. 3 is a diagram illustrating an example of a resource grid of adownlink slot according to the embodiments.

FIG. 4 is a diagram illustrating a structure of an uplink subframeaccording to the embodiments.

FIG. 5 is a diagram illustrating a structure of a downlink subframeaccording to the embodiments.

FIG. 6 is a diagram illustrating an example of a component carrier (CC)and carrier aggregation (CA) used in an LTE-A system.

FIG. 7 illustrates a subframe structure of an LTE-A system according tocross-carrier scheduling.

FIG. 8 is a conceptual diagram illustrating a construction of servingcells according to cross-carrier scheduling.

FIG. 9 illustrates one of methods for transmitting SRS used in theembodiments of the present invention.

FIG. 10 illustrates an example of a subframe to which a cell specificreference signal (CRS) that can be used in the embodiments of thepresent invention is allocated.

FIG. 11 illustrates an example that legacy PDCCH, PDSCH and E-PDCCH,which are used in an LTE/LTE-A system, are multiplexed.

FIG. 12 illustrates an example of a CA environment supported in an LTE-Usystem.

FIG. 13 illustrates one of methods for configuring a TxOP duration.

FIG. 14 illustrates one of methods for configuring CSI-IM transmittedfrom an Scell.

FIG. 15 illustrates another one of methods for configuring CSI-IMtransmitted from an Scell.

FIG. 16 illustrates still another one of methods for configuring CSI-IMtransmitted from an Scell.

FIG. 17 illustrates further still another one of methods for configuringCSI-IM transmitted from an Scell.

FIG. 18 illustrates an example of TxOP subframe configuration when aduration value for interference averaging is set.

FIG. 19 illustrates an example of CDF distribution for interferenceaveraging.

FIG. 20 illustrates one of methods for configuring CSI-IM interworkingwith aperiodic CSI triggering.

FIG. 21 illustrates one of methods for configuring CSI-IM in an eNB andreporting CSI from a UE by using the configured CSI-IM.

FIG. 22 illustrates a method for calculating CSI by means of a UE on thebasis of CSI-IM duration information.

FIG. 23 illustrates a device through which methods described in FIGS. 1to 22 can be implemented.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The embodiments of the present invention, which will hereinafter bedescribed in detail, relates to a wireless access system supporting anunlicensed band, a method for measuring interference on a transmissionopportunity duration, a method for measuring and reporting channel stateinformation by using the method and devices supporting the method.

The embodiments of the present disclosure described below arecombinations of elements and features of the present disclosure inspecific forms. The elements or features may be considered selectiveunless otherwise mentioned. Each element or feature may be practicedwithout being combined with other elements or features. Further, anembodiment of the present disclosure may be constructed by combiningparts of the elements and/or features. Operation orders described inembodiments of the present disclosure may be rearranged. Someconstructions or elements of any one embodiment may be included inanother embodiment and may be replaced with corresponding constructionsor features of another embodiment.

In the description of the attached drawings, a detailed description ofknown procedures or steps of the present disclosure will be avoided lestit should obscure the subject matter of the present disclosure. Inaddition, procedures or steps that could be understood to those skilledin the art will not be described either.

Throughout the specification, when a certain portion “includes” or“comprises” a certain component, this indicates that other componentsare not excluded and may be further included unless otherwise noted. Theterms “unit”, “-or/er” and “module” described in the specificationindicate a unit for processing at least one function or operation, whichmay be implemented by hardware, software or a combination thereof. Inaddition, the terms “a or an”, “one”, “the” etc. may include a singularrepresentation and a plural representation in the context of the presentinvention (more particularly, in the context of the following claims)unless indicated otherwise in the specification or unless contextclearly indicates otherwise.

In the embodiments of the present disclosure, a description is mainlymade of a data transmission and reception relationship between a BaseStation (BS) and a User Equipment (UE). A BS refers to a terminal nodeof a network, which directly communicates with a UE. A specificoperation described as being performed by the BS may be performed by anupper node of the BS.

Namely, it is apparent that, in a network comprised of a plurality ofnetwork nodes including a BS, various operations performed forcommunication with a UE may be performed by the BS, or network nodesother than the BS. The term ‘BS’ may be replaced with a fixed station, aNode B, an evolved Node B (eNode B or eNB), an Advanced Base Station(ABS), an access point, etc.

In the embodiments of the present disclosure, the term terminal may bereplaced with a UE, a Mobile Station (MS), a Subscriber Station (SS), aMobile Subscriber Station (MSS), a mobile terminal, an Advanced MobileStation (AMS), etc.

A transmitter is a fixed and/or mobile node that provides a data serviceor a voice service and a receiver is a fixed and/or mobile node thatreceives a data service or a voice service. Therefore, a UE may serve asa transmitter and a BS may serve as a receiver, on an UpLink (UL).Likewise, the UE may serve as a receiver and the BS may serve as atransmitter, on a DownLink (DL).

The embodiments of the present disclosure may be supported by standardspecifications disclosed for at least one of wireless access systemsincluding an Institute of Electrical and Electronics Engineers (IEEE)802.xx system, a 3^(rd) Generation Partnership Project (3GPP) system, a3GPP Long Term Evolution (LTE) system, and a 3GPP2 system. Inparticular, the embodiments of the present disclosure may be supportedby the standard specifications, 3GPP TS 36.211, 3GPP TS 36.212, 3GPP TS36.213, 3GPP TS 36.321 and 3GPP TS 36.331. That is, the steps or parts,which are not described to clearly reveal the technical idea of thepresent disclosure, in the embodiments of the present disclosure may beexplained by the above standard specifications. All terms used in theembodiments of the present disclosure may be explained by the standardspecifications.

Reference will now be made in detail to the embodiments of the presentdisclosure with reference to the accompanying drawings. The detaileddescription, which will be given below with reference to theaccompanying drawings, is intended to explain exemplary embodiments ofthe present disclosure, rather than to show the only embodiments thatcan be implemented according to the invention.

The following detailed description includes specific terms in order toprovide a thorough understanding of the present disclosure. However, itwill be apparent to those skilled in the art that the specific terms maybe replaced with other terms without departing the technical spirit andscope of the present disclosure.

For example, the term used in embodiments of the present disclosure, adata block is interchangeable with a transport block in the samemeaning. In addition, the MCS/TBS index table used in the LTE/LTE-Asystem can be defined as a first table or a legacy table, and theMCS/TBS index table which is used for supporting the 256QAM can bedefined as a second table or a new table.

The embodiments of the present disclosure can be applied to variouswireless access systems such as Code Division Multiple Access (CDMA),Frequency Division Multiple Access (FDMA), Time Division Multiple Access(TDMA), Orthogonal Frequency Division Multiple Access (OFDMA), SingleCarrier Frequency Division Multiple Access (SC-FDMA), etc.

CDMA may be implemented as a radio technology such as UniversalTerrestrial Radio Access (UTRA) or CDMA2000. TDMA may be implemented asa radio technology such as Global System for Mobile communications(GSM)/General packet Radio Service (GPRS)/Enhanced Data Rates for GSMEvolution (EDGE). OFDMA may be implemented as a radio technology such asIEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Evolved UTRA(E-UTRA), etc.

UTRA is a part of Universal Mobile Telecommunications System (UMTS).3GPP LTE is a part of Evolved UMTS (E-UMTS) using E-UTRA, adopting OFDMAfor DL and SC-FDMA for UL. LTE-Advanced (LTE-A) is an evolution of 3GPPLTE. While the embodiments of the present disclosure are described inthe context of a 3GPP LTE/LTE-A system in order to clarify the technicalfeatures of the present disclosure, the present disclosure is alsoapplicable to an IEEE 802.16e/m system, etc.

1. 3GPP LTE/LTE-A System

In a wireless access system, a UE receives information from an eNB on aDL and transmits information to the eNB on a UL. The informationtransmitted and received between the UE and the eNB includes generaldata information and various types of control information. There aremany physical channels according to the types/usages of informationtransmitted and received between the eNB and the UE.

1.1 System Overview

FIG. 1 illustrates physical channels and a general method using thephysical channels, which may be used in embodiments of the presentdisclosure.

When a UE is powered on or enters a new cell, the UE performs initialcell search (S11). The initial cell search involves acquisition ofsynchronization to an eNB. Specifically, the UE synchronizes its timingto the eNB and acquires information such as a cell Identifier (ID) byreceiving a Primary Synchronization Channel (P-SCH) and a SecondarySynchronization Channel (S-SCH) from the eNB.

Then the UE may acquire information broadcast in the cell by receiving aPhysical Broadcast Channel (PBCH) from the eNB.

During the initial cell search, the UE may monitor a DL channel state byreceiving a Downlink Reference Signal (DL RS).

After the initial cell search, the UE may acquire more detailed systeminformation by receiving a Physical Downlink Control Channel (PDCCH) andreceiving a Physical Downlink Shared Channel (PDSCH) based oninformation of the PDCCH (S12).

To complete connection to the eNB, the UE may perform a random accessprocedure with the eNB (S13 to S16). In the random access procedure, theUE may transmit a preamble on a Physical Random Access Channel (PRACH)(S13) and may receive a PDCCH and a PDSCH associated with the PDCCH(S14). In the case of contention-based random access, the UE mayadditionally perform a contention resolution procedure includingtransmission of an additional PRACH (S15) and reception of a PDCCHsignal and a PDSCH signal corresponding to the PDCCH signal (S16).

After the above procedure, the UE may receive a PDCCH and/or a PDSCHfrom the eNB (S17) and transmit a Physical Uplink Shared Channel (PUSCH)and/or a Physical Uplink Control Channel (PUCCH) to the eNB (S18), in ageneral UL/DL signal transmission procedure.

Control information that the UE transmits to the eNB is genericallycalled Uplink Control Information (UCI). The UCI includes a HybridAutomatic Repeat and reQuest Acknowledgement/Negative Acknowledgement(HARQ-ACK/NACK), a Scheduling Request (SR), a Channel Quality Indicator(CQI), a Precoding Matrix Index (PMI), a Rank Indicator (RI), etc.

In the LTE system, UCI is generally transmitted on a PUCCH periodically.However, if control information and traffic data should be transmittedsimultaneously, the control information and traffic data may betransmitted on a PUSCH. In addition, the UCI may be transmittedaperiodically on the PUSCH, upon receipt of a request/command from anetwork.

FIG. 2 illustrates exemplary radio frame structures used in embodimentsof the present disclosure.

FIG. 2(a) illustrates frame structure type 1. Frame structure type 1 isapplicable to both a full Frequency Division Duplex (FDD) system and ahalf FDD system.

One radio frame is 10 ms (T_(f)=307200·T_(s)) long, includingequal-sized 20 slots indexed from 0 to 19. Each slot is 0.5 ms(T_(slot)=15360·T_(s)) long. One subframe includes two successive slots.An i^(th) subframe includes 2i^(th) and (2i+1)^(th) slots. That is, aradio frame includes 10 subframes. A time required for transmitting onesubframe is defined as a Transmission Time Interval (TTI). T_(s) is asampling time given as T_(s)=1/(15 kHz×2048)=3.2552×10⁻⁸ (about 33 ns).One slot includes a plurality of Orthogonal Frequency DivisionMultiplexing (OFDM) symbols or SC-FDMA symbols in the time domain by aplurality of Resource Blocks (RBs) in the frequency domain.

A slot includes a plurality of OFDM symbols in the time domain. SinceOFDMA is adopted for DL in the 3GPP LTE system, one OFDM symbolrepresents one symbol period. An OFDM symbol may be called an SC-FDMAsymbol or symbol period. An RB is a resource allocation unit including aplurality of contiguous subcarriers in one slot.

In a full FDD system, each of 10 subframes may be used simultaneouslyfor DL transmission and UL transmission during a 10-ms duration. The DLtransmission and the UL transmission are distinguished by frequency. Onthe other hand, a UE cannot perform transmission and receptionsimultaneously in a half FDD system.

The above radio frame structure is purely exemplary. Thus, the number ofsubframes in a radio frame, the number of slots in a subframe, and thenumber of OFDM symbols in a slot may be changed.

FIG. 2(b) illustrates frame structure type 2. Frame structure type 2 isapplied to a Time Division Duplex (TDD) system. One radio frame is 10 ms(T_(f)=307200·T_(s)) long, including two half-frames each having alength of 5 ms (=153600·T_(s)) long. Each half-frame includes fivesubframes each being 1 ms (=30720·T_(s)) long. An i^(th) subframeincludes 2i^(th) and (2i+1)^(th) slots each having a length of 0.5 ms(T_(slot)=15360·T_(s)). T_(s) is a sampling time given as T_(s)=1/(15kHz×2048)=3.2552×10⁻⁸ (about 33 ns).

A type-2 frame includes a special subframe having three fields, DownlinkPilot Time Slot (DwPTS), Guard Period (GP), and Uplink Pilot Time Slot(UpPTS). The DwPTS is used for initial cell search, synchronization, orchannel estimation at a UE, and the UpPTS is used for channel estimationand UL transmission synchronization with a UE at an eNB. The GP is usedto cancel UL interference between a UL and a DL, caused by themulti-path delay of a DL signal.

[Table 1] below lists special subframe configurations (DwPTS/GP/UpPTSlengths).

TABLE 1 Normal cyclic prefix in downlink UpPTS Extended cyclic prefix indownlink Normal Extended UpPTS Special subframe cyclic prefix cyclicprefix Normal cyclic Extended cyclic configuration DwPTS in uplink inuplink DwPTS prefix in uplink prefix in uplink 0  6592 · T_(s) 2192 ·T_(s) 2560 · T_(s)  7680 · T_(s) 2192 · T_(s) 2560 · T_(s) 1 19760 ·T_(s) 20480 · T_(s) 2 21952 · T_(s) 23040 · T_(s) 3 24144 · T_(s) 25600· T_(s) 4 26336 · T_(s)  7680 · T_(s) 4384 · T_(s) 5120 · T_(s) 5  6592· T_(s) 4384 · T_(s) 5120 · T_(s) 20480 · T_(s) 6 19760 · T_(s) 23040 ·T_(s) 7 21952 · T_(s) — — — 8 24144 · T_(s) — — —

FIG. 3 illustrates an exemplary structure of a DL resource grid for theduration of one DL slot, which may be used in embodiments of the presentdisclosure.

Referring to FIG. 3, a DL slot includes a plurality of OFDM symbols inthe time domain. One DL slot includes 7 OFDM symbols in the time domainand an RB includes 12 subcarriers in the frequency domain, to which thepresent disclosure is not limited.

Each element of the resource grid is referred to as a Resource Element(RE). An RB includes 12×7 REs. The number of RBs in a DL slot, N_(DL)depends on a DL transmission bandwidth. A UL slot may have the samestructure as a DL slot.

FIG. 4 illustrates a structure of a UL subframe which may be used inembodiments of the present disclosure.

Referring to FIG. 4, a UL subframe may be divided into a control regionand a data region in the frequency domain. A PUCCH carrying UCI isallocated to the control region and a PUSCH carrying user data isallocated to the data region. To maintain a single carrier property, aUE does not transmit a PUCCH and a PUSCH simultaneously. A pair of RBsin a subframe are allocated to a PUCCH for a UE. The RBs of the RB pairoccupy different subcarriers in two slots. Thus it is said that the RBpair frequency-hops over a slot boundary.

FIG. 5 illustrates a structure of a DL subframe that may be used inembodiments of the present disclosure.

Referring to FIG. 5, up to three OFDM symbols of a DL subframe, startingfrom OFDM symbol 0 are used as a control region to which controlchannels are allocated and the other OFDM symbols of the DL subframe areused as a data region to which a PDSCH is allocated. DL control channelsdefined for the 3GPP LTE system include a Physical Control FormatIndicator Channel (PCFICH), a PDCCH, and a Physical Hybrid ARQ IndicatorChannel (PHICH).

The PCFICH is transmitted in the first OFDM symbol of a subframe,carrying information about the number of OFDM symbols used fortransmission of control channels (i.e. the size of the control region)in the subframe. The PHICH is a response channel to a UL transmission,delivering an HARQ ACK/NACK signal. Control information carried on thePDCCH is called Downlink Control Information (DCI). The DCI transportsUL resource assignment information, DL resource assignment information,or UL Transmission (Tx) power control commands for a UE group.

1.2 Physical Downlink Control Channel (PDCCH)

1.2.1 PDCCH Overview

The PDCCH may deliver information about resource allocation and atransport format for a Downlink Shared Channel (DL-SCH) (i.e. a DLgrant), information about resource allocation and a transport format foran Uplink Shared Channel (UL-SCH) (i.e. a UL grant), paging informationof a Paging Channel (PCH), system information on the DL-SCH, informationabout resource allocation for a higher-layer control message such as arandom access response transmitted on the PDSCH, a set of Tx powercontrol commands for individual UEs of a UE group, Voice Over InternetProtocol (VoIP) activation indication information, etc.

A plurality of PDCCHs may be transmitted in the control region. A UE maymonitor a plurality of PDCCHs. A PDCCH is transmitted in an aggregate ofone or more consecutive Control Channel Elements (CCEs). A PDCCH made upof one or more consecutive CCEs may be transmitted in the control regionafter subblock interleaving. A CCE is a logical allocation unit used toprovide a PDCCH at a code rate based on the state of a radio channel. ACCE includes a plurality of RE Groups (REGs). The format of a PDCCH andthe number of available bits for the PDCCH are determined according tothe relationship between the number of CCEs and a code rate provided bythe CCEs.

1.2.2 PDCCH Structure

A plurality of PDCCHs for a plurality of UEs may be multiplexed andtransmitted in the control region. A PDCCH is made up of an aggregate ofone or more consecutive CCEs. A CCE is a unit of 9 REGs each REGincluding 4 REs. Four Quadrature Phase Shift Keying (QPSK) symbols aremapped to each REG. REs occupied by RSs are excluded from REGs. That is,the total number of REGs in an OFDM symbol may be changed depending onthe presence or absence of a cell-specific RS. The concept of an REG towhich four REs are mapped is also applicable to other DL controlchannels (e.g. the PCFICH or the PHICH). Let the number of REGs that arenot allocated to the PCFICH or the PHICH be denoted by N_(REG). Then thenumber of CCEs available to the system is N_(CCE) (=└N_(REG)/9┘) and theCCEs are indexed from 0 to N_(CCE)−1.

To simplify the decoding process of a UE, a PDCCH format including nCCEs may start with a CCE having an index equal to a multiple of n. Thatis, given CCE i, the PDCCH format may start with a CCE satisfying i modn=0.

The eNB may configure a PDCCH with 1, 2, 4, or 8 CCEs. {1, 2, 4, 8} arecalled CCE aggregation levels. The number of CCEs used for transmissionof a PDCCH is determined according to a channel state by the eNB. Forexample, one CCE is sufficient for a PDCCH directed to a UE in a good DLchannel state (a UE near to the eNB). On the other hand, 8 CCEs may berequired for a PDCCH directed to a UE in a poor DL channel state (a UEat a cell edge) in order to ensure sufficient robustness.

[Table 2] below illustrates PDCCH formats. 4 PDCCH formats are supportedaccording to CCE aggregation levels as illustrated in [Table 2].

TABLE 2 PDCCH Number of Number of Number of format CCEs (n) REGs PDCCHbits 0 1 9 72 1 2 18 144 2 4 36 288 3 8 72 576

A different CCE aggregation level is allocated to each UE because theformat or Modulation and Coding Scheme (MCS) level of controlinformation delivered in a PDCCH for the UE is different. An MCS leveldefines a code rate used for data coding and a modulation order. Anadaptive MCS level is used for link adaptation. In general, three orfour MCS levels may be considered for control channels carrying controlinformation.

Regarding the formats of control information, control informationtransmitted on a PDCCH is called DCI. The configuration of informationin PDCCH payload may be changed depending on the DCI format. The PDCCHpayload is information bits. [Table 3] lists DCI according to DCIformats.

TABLE 3 DCI Format Description Format Resource grants for PUSCHtransmissions (uplink) 0 Format Resource assignments for single codewordPDSCH 1 transmissions (transmission modes 1, 2 and 7) Format Compactsignaling of resource assignments for single 1A codeword PDSCH (allmodes) Format Compact resource assignments for PDSCH using rank-1 closed1B loop precoding (mode 6) Format Very compact resource assignments forPDSCH (e.g., 1C paging/broadcast system information) Format Compactresource assignments for PDSCH using multi-user 1D MIMO (mode 5) FormatResource assignments for PDSCH for closed-loop MIMO 2 operation (mode 4)Format Resource assignments for PDSCH for open-loop MIMO 2A operation(mode 3) Format Power control commands for PUCCH and PUSCH with 2-bit/1-3/3A bit power adjustment Format Scheduling of PUSCH in one UL cell withmulti-antenna port 4 transmission mode

Referring to [Table 3], the DCI formats include Format 0 for PUSCHscheduling, Format 1 for single-codeword PDSCH scheduling, Format 1A forcompact single-codeword PDSCH scheduling, Format 1C for very compactDL-SCH scheduling, Format 2 for PDSCH scheduling in a closed-loopspatial multiplexing mode, Format 2A for PDSCH scheduling in anopen-loop spatial multiplexing mode, and Format 3/3A for transmission ofTransmission Power Control (TPC) commands for uplink channels. DCIFormat 1A is available for PDSCH scheduling irrespective of thetransmission mode of a UE.

The length of PDCCH payload may vary with DCI formats. In addition, thetype and length of PDCCH payload may be changed depending on compact ornon-compact scheduling or the transmission mode of a UE.

The transmission mode of a UE may be configured for DL data reception ona PDSCH at the UE. For example, DL data carried on a PDSCH includesscheduled data, a paging message, a random access response, broadcastinformation on a BCCH, etc. for a UE. The DL data of the PDSCH isrelated to a DCI format signaled through a PDCCH. The transmission modemay be configured semi-statically for the UE by higher-layer signaling(e.g. Radio Resource Control (RRC) signaling). The transmission mode maybe classified as single antenna transmission or multi-antennatransmission.

A transmission mode is configured for a UE semi-statically byhigher-layer signaling. For example, multi-antenna transmission schememay include transmit diversity, open-loop or closed-loop spatialmultiplexing, Multi-User Multiple Input Multiple Output (MU-MIMO), orbeamforming. Transmit diversity increases transmission reliability bytransmitting the same data through multiple Tx antennas. Spatialmultiplexing enables high-speed data transmission without increasing asystem bandwidth by simultaneously transmitting different data throughmultiple Tx antennas. Beamforming is a technique of increasing theSignal to Interference plus Noise Ratio (SINR) of a signal by weightingmultiple antennas according to channel states.

A DCI format for a UE depends on the transmission mode of the UE. The UEhas a reference DCI format monitored according to the transmission modeconfigure for the UE. The following 10 transmission modes are availableto UEs:

(1) Transmission mode 1: Single antenna port (port 0);

(2) Transmission mode 2: Transmit diversity;

(3) Transmission mode 3: Open-loop spatial multiplexing when the numberof layer is larger than 1 or Transmit diversity when the rank is 1;

(4) Transmission mode 4: Closed-loop spatial multiplexing;

(5) Transmission mode 5: MU-MIMO;

(6) Transmission mode 6: Closed-loop rank-1 precoding;

(7) Transmission mode 7: Precoding supporting a single layertransmission, which is not based on a codebook (Rel-8);

(8) Transmission mode 8: Precoding supporting up to two layers, whichare not based on a codebook (Rel-9);

(9) Transmission mode 9: Precoding supporting up to eight layers, whichare not based on a codebook (Rel-10); and

(10) Transmission mode 10: Precoding supporting up to eight layers,which are not based on a codebook, used for CoMP (Rel-11).

1.2.3 PDCCH Transmission

The eNB determines a PDCCH format according to DCI that will betransmitted to the UE and adds a Cyclic Redundancy Check (CRC) to thecontrol information. The CRC is masked by a unique Identifier (ID) (e.g.a Radio Network Temporary Identifier (RNTI)) according to the owner orusage of the PDCCH. If the PDCCH is destined for a specific UE, the CRCmay be masked by a unique ID (e.g. a cell-RNTI (C-RNTI)) of the UE. Ifthe PDCCH carries a paging message, the CRC of the PDCCH may be maskedby a paging indicator ID (e.g. a Paging-RNTI (P-RNTI)). If the PDCCHcarries system information, particularly, a System Information Block(SIB), its CRC may be masked by a system information ID (e.g. a SystemInformation RNTI (SI-RNTI)). To indicate that the PDCCH carries a randomaccess response to a random access preamble transmitted by a UE, its CRCmay be masked by a Random Access-RNTI (RA-RNTI).

Then, the eNB generates coded data by channel-encoding the CRC-addedcontrol information. The channel coding may be performed at a code ratecorresponding to an MCS level. The eNB rate-matches the coded dataaccording to a CCE aggregation level allocated to a PDCCH format andgenerates modulation symbols by modulating the coded data. Herein, amodulation order corresponding to the MCS level may be used for themodulation. The CCE aggregation level for the modulation symbols of aPDCCH may be one of 1, 2, 4, and 8. Subsequently, the eNB maps themodulation symbols to physical REs (i.e. CCE to RE mapping).

1.2.4 Blind Decoding (BD)

A plurality of PDCCHs may be transmitted in a subframe. That is, thecontrol region of a subframe includes a plurality of CCEs, CCE 0 to CCEN_(CCE,k)−1. N_(CCE,k) is the total number of CCEs in the control regionof a k^(th) subframe. A UE monitors a plurality of PDCCHs in everysubframe. This means that the UE attempts to decode each PDCCH accordingto a monitored PDCCH format.

The eNB does not provide the UE with information about the position of aPDCCH directed to the UE in an allocated control region of a subframe.Without knowledge of the position, CCE aggregation level, or DCI formatof its PDCCH, the UE searches for its PDCCH by monitoring a set of PDCCHcandidates in the subframe in order to receive a control channel fromthe eNB. This is called blind decoding. Blind decoding is the process ofdemasking a CRC part with a UE ID, checking a CRC error, and determiningwhether a corresponding PDCCH is a control channel directed to a UE bythe UE.

The UE monitors a PDCCH in every subframe to receive data transmitted tothe UE in an active mode. In a Discontinuous Reception (DRX) mode, theUE wakes up in a monitoring interval of every DRX cycle and monitors aPDCCH in a subframe corresponding to the monitoring interval. ThePDCCH-monitored subframe is called a non-DRX subframe.

To receive its PDCCH, the UE should blind-decode all CCEs of the controlregion of the non-DRX subframe. Without knowledge of a transmitted PDCCHformat, the UE should decode all PDCCHs with all possible CCEaggregation levels until the UE succeeds in blind-decoding a PDCCH inevery non-DRX subframe. Since the UE does not know the number of CCEsused for its PDCCH, the UE should attempt detection with all possibleCCE aggregation levels until the UE succeeds in blind decoding of aPDCCH.

In the LTE system, the concept of Search Space (SS) is defined for blinddecoding of a UE. An SS is a set of PDCCH candidates that a UE willmonitor. The SS may have a different size for each PDCCH format. Thereare two types of SSs, Common Search Space (CSS) andUE-specific/Dedicated Search Space (USS).

While all UEs may know the size of a CSS, a USS may be configured foreach individual UE. Accordingly, a UE should monitor both a CSS and aUSS to decode a PDCCH. As a consequence, the UE performs up to 44 blinddecodings in one subframe, except for blind decodings based on differentCRC values (e.g., C-RNTI, P-RNTI, SI-RNTI, and RA-RNTI).

In view of the constraints of an SS, the eNB may not secure CCEresources to transmit PDCCHs to all intended UEs in a given subframe.This situation occurs because the remaining resources except forallocated CCEs may not be included in an SS for a specific UE. Tominimize this obstacle that may continue in the next subframe, aUE-specific hopping sequence may apply to the starting point of a USS.

[Table 4] illustrates the sizes of CSSs and USSs.

TABLE 4 PDCCH Number of Number of candidates Number of candidates FormatCCEs (n) in common search space in dedicated search space 0 1 — 6 1 2 —6 2 4 4 2 3 8 2 2

To mitigate the load of the UE caused by the number of blind decodingattempts, the UE does not search for all defined DCI formatssimultaneously. Specifically, the UE always searches for DCI Format 0and DCI Format 1A in a USS. Although DCI Format 0 and DCI Format 1A areof the same size, the UE may distinguish the DCI formats by a flag forformat 0/format 1a differentiation included in a PDCCH. Other DCIformats than DCI Format 0 and DCI Format 1A, such as DCI Format 1, DCIFormat 1B, and DCI Format 2 may be required for the UE.

The UE may search for DCI Format 1A and DCI Format 1C in a CSS. The UEmay also be configured to search for DCI Format 3 or 3A in the CSS.Although DCI Format 3 and DCI Format 3A have the same size as DCI Format0 and DCI Format 1A, the UE may distinguish the DCI formats by a CRCscrambled with an ID other than a UE-specific ID.

An SS S_(k) ^((L)) is a PDCCH candidate set with a CCE aggregation levelL∈{1,2,4,8}. The CCEs of PDCCH candidate set m in the SS may bedetermined by the following equation.

L·{(Y _(k) +m)mod └N _(CCE,k) /L┘}+i  [Equation 1]

-   -   where M^((L)) is the number of PDCCH candidates with CCE        aggregation level L to be monitored in the SS, m=0, Λ, M^((L))−1        i is the index of a CCE in each PDCCH candidate, and i=0, Λ,        L−1. k=└n_(s)/2┘ where n_(s) is the index of a slot in a radio        frame.

As described before, the UE monitors both the USS and the CSS to decodea PDCCH. The CSS supports PDCCHs with CCE aggregation levels {4, 8} andthe USS supports PDCCHs with CCE aggregation levels {1, 2, 4, 8}. [Table5] illustrates PDCCH candidates monitored by a UE.

TABLE 5 Search space S_(k) ^((L)) Number of PDCCH Type Aggregation levelL Size [in CCEs] candidates M^((L)) UE-specific 1 6 6 2 12 6 4 8 2 8 162 Common 4 16 4 8 16 2

Referring to [Equation 1], for two aggregation levels, L=4 and L=8,Y_(k) is set to 0 in the CSS, whereas Y_(k) is defined by [Equation 2]for aggregation level L in the USS.

Y _(k)=(A·Y _(k-1))mod D  [Equation 2]

where Y⁻¹=n_(RNTI)≠0, n_(RNTI) indicating an RNTI value. A=39827 andD=65537.

2. Carrier Aggregation (CA) Environment

2.1 CA Overview

A 3GPP LTE system (conforming to Rel-8 or Rel-9) (hereinafter, referredto as an LTE system) uses Multi-Carrier Modulation (MCM) in which asingle Component Carrier (CC) is divided into a plurality of bands. Incontrast, a 3GPP LTE-A system (hereinafter, referred to an LTE-A system)may use CA by aggregating one or more CCs to support a broader systembandwidth than the LTE system. The term CA is interchangeably used withcarrier combining, multi-CC environment, or multi-carrier environment.

In the present disclosure, multi-carrier means CA (or carriercombining). Herein, CA covers aggregation of contiguous carriers andaggregation of non-contiguous carriers. The number of aggregated CCs maybe different for a DL and a UL. If the number of DL CCs is equal to thenumber of UL CCs, this is called symmetric aggregation. If the number ofDL CCs is different from the number of UL CCs, this is called asymmetricaggregation. The term CA is interchangeable with carrier combining,bandwidth aggregation, spectrum aggregation, etc.

The LTE-A system aims to support a bandwidth of up to 100 MHz byaggregating two or more CCs, that is, by CA. To guarantee backwardcompatibility with a legacy IMT system, each of one or more carriers,which has a smaller bandwidth than a target bandwidth, may be limited toa bandwidth used in the legacy system.

For example, the legacy 3GPP LTE system supports bandwidths {1.4, 3, 5,10, 15, and 20 MHz} and the 3GPP LTE-A system may support a broaderbandwidth than 20 MHz using these LTE bandwidths. A CA system of thepresent disclosure may support CA by defining a new bandwidthirrespective of the bandwidths used in the legacy system.

There are two types of CA, intra-band CA and inter-band CA. Intra-bandCA means that a plurality of DL CCs and/or UL CCs are successive oradjacent in frequency. In other words, the carrier frequencies of the DLCCs and/or UL CCs are positioned in the same band. On the other hand, anenvironment where CCs are far away from each other in frequency may becalled inter-band CA. In other words, the carrier frequencies of aplurality of DL CCs and/or UL CCs are positioned in different bands. Inthis case, a UE may use a plurality of Radio Frequency (RF) ends toconduct communication in a CA environment.

The LTE-A system adopts the concept of cell to manage radio resources.The above-described CA environment may be referred to as a multi-cellenvironment. A cell is defined as a pair of DL and UL CCs, although theUL resources are not mandatory. Accordingly, a cell may be configuredwith DL resources alone or DL and UL resources.

For example, if one serving cell is configured for a specific UE, the UEmay have one DL CC and one UL CC. If two or more serving cells areconfigured for the UE, the UE may have as many DL CCs as the number ofthe serving cells and as many UL CCs as or fewer UL CCs than the numberof the serving cells, or vice versa. That is, if a plurality of servingcells are configured for the UE, a CA environment using more UL CCs thanDL CCs may also be supported.

CA may be regarded as aggregation of two or more cells having differentcarrier frequencies (center frequencies). Herein, the term ‘cell’ shouldbe distinguished from ‘cell’ as a geographical area covered by an eNB.Hereinafter, intra-band CA is referred to as intra-band multi-cell andinter-band CA is referred to as inter-band multi-cell.

In the LTE-A system, a Primacy Cell (PCell) and a Secondary Cell (SCell)are defined. A PCell and an SCell may be used as serving cells. For a UEin RRC_CONNECTED state, if CA is not configured for the UE or the UEdoes not support CA, a single serving cell including only a PCell existsfor the UE. On the contrary, if the UE is in RRC_CONNECTED state and CAis configured for the UE, one or more serving cells may exist for theUE, including a PCell and one or more SCells.

Serving cells (PCell and SCell) may be configured by an RRC parameter. Aphysical-layer ID of a cell, PhysCellId is an integer value ranging from0 to 503. A short ID of an SCell, SCellIndex is an integer value rangingfrom 1 to 7. A short ID of a serving cell (PCell or SCell),ServeCellIndex is an integer value ranging from 1 to 7. IfServeCellIndex is 0, this indicates a PCell and the values ofServeCellIndex for SCells are pre-assigned. That is, the smallest cellID (or cell index) of ServeCellIndex indicates a PCell.

A PCell refers to a cell operating in a primary frequency (or a primaryCC). A UE may use a PCell for initial connection establishment orconnection reestablishment. The PCell may be a cell indicated duringhandover. In addition, the PCell is a cell responsible forcontrol-related communication among serving cells configured in a CAenvironment. That is, PUCCH allocation and transmission for the UE maytake place only in the PCell. In addition, the UE may use only the PCellin acquiring system information or changing a monitoring procedure. AnEvolved Universal Terrestrial Radio Access Network (E-UTRAN) may changeonly a PCell for a handover procedure by a higher-layerRRCConnectionReconfiguration message including mobilityControlInfo to aUE supporting CA.

An SCell may refer to a cell operating in a secondary frequency (or asecondary CC). Although only one PCell is allocated to a specific UE,one or more SCells may be allocated to the UE. An SCell may beconfigured after RRC connection establishment and may be used to provideadditional radio resources. There is no PUCCH in cells other than aPCell, that is, in SCells among serving cells configured in the CAenvironment.

When the E-UTRAN adds an SCell to a UE supporting CA, the E-UTRAN maytransmit all system information related to operations of related cellsin RRC_CONNECTED state to the UE by dedicated signaling. Changing systeminformation may be controlled by releasing and adding a related SCell.Herein, a higher-layer RRCConnectionReconfiguration message may be used.The E-UTRAN may transmit a dedicated signal having a different parameterfor each cell rather than it broadcasts in a related SCell.

After an initial security activation procedure starts, the E-UTRAN mayconfigure a network including one or more SCells by adding the SCells toa PCell initially configured during a connection establishmentprocedure. In the CA environment, each of a PCell and an SCell mayoperate as a CC. Hereinbelow, a Primary CC (PCC) and a PCell may be usedin the same meaning and a Secondary CC (SCC) and an SCell may be used inthe same meaning in embodiments of the present disclosure.

FIG. 6 illustrates an example of CCs and CA in the LTE-A system, whichare used in embodiments of the present disclosure.

FIG. 6(a) illustrates a single carrier structure in the LTE system.There are a DL CC and a UL CC and one CC may have a frequency range of20 MHz.

FIG. 6(b) illustrates a CA structure in the LTE-A system. In theillustrated case of FIG. 6(b), three CCs each having 20 MHz areaggregated. While three DL CCs and three UL CCs are configured, thenumbers of DL CCs and UL CCs are not limited. In CA, a UE may monitorthree CCs simultaneously, receive a DL signal/DL data in the three CCs,and transmit a UL signal/UL data in the three CCs.

If a specific cell manages N DL CCs, the network may allocate M (M≤N) DLCCs to a UE. The UE may monitor only the M DL CCs and receive a DLsignal in the M DL CCs. The network may prioritize L (L≤M≤N) DL CCs andallocate a main DL CC to the UE. In this case, the UE should monitor theL DL CCs. The same thing may apply to UL transmission.

The linkage between the carrier frequencies of DL resources (or DL CCs)and the carrier frequencies of UL resources (or UL CCs) may be indicatedby a higher-layer message such as an RRC message or by systeminformation. For example, a set of DL resources and UL resources may beconfigured based on linkage indicated by System Information Block Type 2(SIB2). Specifically, DL-UL linkage may refer to a mapping relationshipbetween a DL CC carrying a PDCCH with a UL grant and a UL CC using theUL grant, or a mapping relationship between a DL CC (or a UL CC)carrying HARQ data and a UL CC (or a DL CC) carrying an HARQ ACK/NACKsignal.

2.2 Cross Carrier Scheduling

Two scheduling schemes, self-scheduling and cross carrier scheduling aredefined for a CA system, from the perspective of carriers or servingcells. Cross carrier scheduling may be called cross CC scheduling orcross cell scheduling.

In self-scheduling, a PDCCH (carrying a DL grant) and a PDSCH aretransmitted in the same DL CC or a PUSCH is transmitted in a UL CClinked to a DL CC in which a PDCCH (carrying a UL grant) is received.

In cross carrier scheduling, a PDCCH (carrying a DL grant) and a PDSCHare transmitted in different DL CCs or a PUSCH is transmitted in a UL CCother than a UL CC linked to a DL CC in which a PDCCH (carrying a ULgrant) is received.

Cross carrier scheduling may be activated or deactivated UE-specificallyand indicated to each UE semi-statically by higher-layer signaling (e.g.RRC signaling).

If cross carrier scheduling is activated, a Carrier Indicator Field(CIF) is required in a PDCCH to indicate a DL/UL CC in which aPDSCH/PUSCH indicated by the PDCCH is to be transmitted. For example,the PDCCH may allocate PDSCH resources or PUSCH resources to one of aplurality of CCs by the CIF. That is, when a PDCCH of a DL CC allocatesPDSCH or PUSCH resources to one of aggregated DL/UL CCs, a CIF is set inthe PDCCH. In this case, the DCI formats of LTE Release-8 may beextended according to the CIF. The CIF may be fixed to three bits andthe position of the CIF may be fixed irrespective of a DCI format size.In addition, the LTE Release-8 PDCCH structure (the same coding andresource mapping based on the same CCEs) may be reused.

On the other hand, if a PDCCH transmitted in a DL CC allocates PDSCHresources of the same DL CC or allocates PUSCH resources in a single ULCC linked to the DL CC, a CIF is not set in the PDCCH. In this case, theLTE Release-8 PDCCH structure (the same coding and resource mappingbased on the same CCEs) may be used.

If cross carrier scheduling is available, a UE needs to monitor aplurality of PDCCHs for DCI in the control region of a monitoring CCaccording to the transmission mode and/or bandwidth of each CC.Accordingly, an appropriate SS configuration and PDCCH monitoring areneeded for the purpose.

In the CA system, a UE DL CC set is a set of DL CCs scheduled for a UEto receive a PDSCH, and a UE UL CC set is a set of UL CCs scheduled fora UE to transmit a PUSCH. A PDCCH monitoring set is a set of one or moreDL CCs in which a PDCCH is monitored. The PDCCH monitoring set may beidentical to the UE DL CC set or may be a subset of the UE DL CC set.The PDCCH monitoring set may include at least one of the DL CCs of theUE DL CC set. Or the PDCCH monitoring set may be defined irrespective ofthe UE DL CC set. DL CCs included in the PDCCH monitoring set may beconfigured to always enable self-scheduling for UL CCs linked to the DLCCs. The UE DL CC set, the UE UL CC set, and the PDCCH monitoring setmay be configured UE-specifically, UE group-specifically, orcell-specifically.

If cross carrier scheduling is deactivated, this implies that the PDCCHmonitoring set is always identical to the UE DL CC set. In this case,there is no need for signaling the PDCCH monitoring set. However, ifcross carrier scheduling is activated, the PDCCH monitoring set may bedefined within the UE DL CC set. That is, the eNB transmits a PDCCH onlyin the PDCCH monitoring set to schedule a PDSCH or PUSCH for the UE.

FIG. 7 illustrates a cross carrier-scheduled subframe structure in theLTE-A system, which is used in embodiments of the present disclosure.

Referring to FIG. 7, three DL CCs are aggregated for a DL subframe forLTE-A UEs. DL CC ‘A’ is configured as a PDCCH monitoring DL CC. If a CIFis not used, each DL CC may deliver a PDCCH that schedules a PDSCH inthe same DL CC without a CIF. On the other hand, if the CIF is used byhigher-layer signaling, only DL CC ‘A’ may carry a PDCCH that schedulesa PDSCH in the same DL CC ‘A’ or another CC. Herein, no PDCCH istransmitted in DL CC ‘B’ and DL CC ‘C’ that are not configured as PDCCHmonitoring DL CCs.

FIG. 8 is conceptual diagram illustrating a construction of servingcells according to cross-carrier scheduling.

Referring to FIG. 8, an eNB (or BS) and/or UEs for use in a radio accesssystem supporting carrier aggregation (CA) may include one or moreserving cells. In FIG. 8, the eNB can support a total of four servingcells (cells A, B, C and D). It is assumed that UE A may include Cells(A, B, C), UE B may include Cells (B, C, D), and UE C may include CellB. In this case, at least one of cells of each UE may be composed ofPcell. In this case, Pcell is always activated, and Scell may beactivated or deactivated by the eNB and/or UE.

The cells shown in FIG. 8 may be configured per UE. The above-mentionedcells selected from among cells of the eNB, cell addition may be appliedto carrier aggregation (CA) on the basis of a measurement report messagereceived from the UE. The configured cell may reserve resources forACK/NACK message transmission in association with PDSCH signaltransmission. The activated cell is configured to actually transmit aPDSCH signal and/or a PUSCH signal from among the configured cells, andis configured to transmit CSI reporting and Sounding Reference Signal(SRS) transmission. The deactivated cell is configured not totransmit/receive PDSCH/PUSCH signals by an eNB command or a timeroperation, and CRS reporting and SRS transmission are interrupted.

2.3 CA Environment Based CoMP Operation

Hereinafter, a cooperation multi-point (CoMP) transmission operationapplicable to the embodiments of the present invention will bedescribed.

In the LTE-A system, CoMP transmission may be implemented using acarrier aggregation (CA) function in the LTE. FIG. 9 is a conceptualview illustrating a CoMP system operated based on a CA environment.

In FIG. 9, it is assumed that a carrier operated as a Pcell and acarrier operated as an Scell may use the same frequency band on afrequency axis and are allocated to two eNBs geographically spaced apartfrom each other. At this time, a serving eNB of UE1 may be allocated tothe Pcell, and a neighboring cell causing much interference may beallocated to the Scell. That is, the eNB of the Pcell and the eNB of theScell may perform various DL/UL CoMP operations such as jointtransmission (JT), CS/CB and dynamic cell selection for one UE.

FIG. 9 illustrates an example that cells managed by two eNBs areaggregated as Pcell and Scell with respect to one UE (e.g., UE1).However, as another example, three or more cells may be aggregated. Forexample, some cells of three or more cells may be configured to performCoMP operation for one UE in the same frequency band, and the othercells may be configured to perform simple CA operation in differentfrequency bands. At this time, the Pcell does not always need toparticipate in CoMP operation.

2. 4 Reference Signal (RS)

Hereinafter, reference signals that can be used in the embodiments ofthe present invention will be described.

FIG. 10 illustrates an example of a subframe to which a cell specificreference signal (CRS) that can be used in the embodiments of thepresent invention is allocated.

FIG. 10 illustrates an allocation structure of a CRS if four antennasare supported in a wireless access system. In a 3GPP LTE/LTE-A system,the CRS is used for decoding and channel state measurement. Therefore,the CRS is transmitted to all downlink bandwidths at all downlinksubframes within a cell supporting PDSCH transmission, and istransmitted from all antenna ports configured in an eNB.

In more detail, CRS sequence is mapped to complex-valued modulationsymbols used as reference symbols for an antenna port p at a slot n_(s).

A UE may measure CSI by using the CRS, and may decode a downlink datasignal received through a PDSCH at a subframe including the CRS, byusing the CRS. That is, the eNB transmits the CRS from all RBs to acertain position within each RB, and the UE detects a PDSCH afterperforming channel estimation based on the CRS. For example, the UEmeasures a signal received at a CRS RE. The UE may detect a PDSCH signalfrom RE to which PDSCH is mapped, by using a ratio of receiving energyper CRS RE and a receiving energy per RE to which PDSCH is mapped.

As described above, if the PDSCH signal is transmitted based on the CRS,since the eNB should transmit the CRS to all RBs, unnecessary RSoverhead is generated. To solve this problem, the 3GPP LTE-A systemadditionally defines UE-specific RS (hereinafter, UE-RS) and channelstate information reference signal (CSI-RS) in addition to the CRS. TheUE-RS is used for demodulation, and the CSI-RS is used to derive channelstate information.

Since the UE-RS and the CRS are used for demodulation, they may be RSsfor demodulation in view of use. That is, the UE-RS may be regarded as akind of a demodulation reference signal (DM-RS). Also, since the CSI-RSand the CRS are used for channel measurement or channel estimation, theymay be regarded as RSs for channel state measurement in view of use.

2. 5 Enhanced PDCCH (EPDCCH)

In the 3GPP LTE/LTE-A system, cross carrier scheduling (CC S) in anaggregation status for a plurality of component carriers (CC: componentcarrier=(serving) cell) will be defined. One scheduled CC may previouslybe configured to be DL/UL scheduled from another one scheduling CC (thatis, to receive DL/UL grant PDCCH for a corresponding scheduled CC). Atthis time, the scheduling CC may basically perform DL/UL scheduling foritself. In other words, a search space (SS) for a PDCCH for schedulingscheduling/scheduled CCs which are in the CCS relation may exist in acontrol channel region of all the scheduling CCs.

Meanwhile, in the LTE system, FDD DL carrier or TDD DL subframes areconfigured to use first n (n<=4) OFDM symbols of each subframe fortransmission of physical channels for transmission of various kinds ofcontrol information, wherein examples of the physical channels include aPDCCH, a PHICH, and a PCFICH. At this time, the number of OFDM symbolsused for control channel transmission at each subframe may be deliveredto the UE dynamically through a physical channel such as PCFICH orsemi-statically through RRC signaling.

Meanwhile, in the LTE/LTE-A system, since a PDCCH which is a physicalchannel for DL/UL scheduling and transmitting various kinds of controlinformation has a limitation that it is transmitted through limited OFDMsymbols, enhanced PDCCH (i.e., E-PDCCH) multiplexed with a PDSCH morefreely in a way of FDM/TDM may be introduced instead of a controlchannel such as PDCCH, which is transmitted through OFDM symbol andseparated from PDSCH. FIG. 11 illustrates an example that legacy PDCCH,PDSCH and E-PDCCH, which are used in an LTE/LTE-A system, aremultiplexed.

2.6 CSI Feedback on PUCCH

First of all, in the 3GPP LTE system, when a DL reception entity (e.g.,a UE) is connected to a DL transmission entity (e.g., a BS), the DLreception entity performs measurement on a Reference Signal ReceivedPower (RSRP) of a reference signal transmitted in DL, a quality of areference signal Reference Signal Received Quality (RSRQ) and the likeat a random time and is then able to make a periodic or even-triggeredreport of a corresponding measurement result to the base station.

Each UE reports a DL channel information in accordance with a DL channelstatus via uplink. A base station is then able to determinetime/frequency resources, MCS and the like appropriate for a datatransmission to each UE using the DL channel information received fromthe each UE.

Such CSI may include CQI, Precoding Matrix Indicator (PMI), PrecoderType Indication (PTI) and/or Rank Indication (RI). In particular, theCSI may be transmitted entirely or partially depending on a transmissionmode of each UE. CQI is determined based on a received signal quality ofa UE, which may be generally determined on the basis of a measurement ofa DL reference signal. In doing so, a CQI value actually delivered to abase station may correspond to an MCS capable of providing maximumperformance by maintaining a Block Error Rate (BLER) under 10% in thereceived signal quality measured by a UE.

This channel information reporting may be classified into a periodicreport transmitted periodically and an aperiodic report transmitted inresponse to a request made by a base station.

In case of the aperiodic report, it is set for each UE by a 1-bitrequest bit (CQI request bit) contained in UL scheduling informationdownloaded to a UE by a base station. Having received this information,each UE is then able to deliver channel information to the base stationvia a physical uplink shared channel (PUSCH) in consideration of itstransmission mode. And, it may set RI and CQI/PMI not to be transmittedon the same PUSCH.

In case of the periodic report, a period for transmitting channelinformation via an upper layer signal, an offset in the correspondingperiod and the like are signaled to each UE by subframe unit and channelinformation in consideration of a transmission mode of each UE may bedelivered to a base station via a physical uplink control channel(PUCCH) in accordance with a determined period. In case that datatransmitted in uplink simultaneously exists in a subframe in whichchannel information is transmitted by a determined period, thecorresponding channel information may be transmitted together with thedata not on the PUCCH but on a PUSCH. In case of the periodic report viaPUCCH, bits (e.g., 11 bits) limited further than those of the PUSCH maybe used. RI and CQI/PMI may be transmitted on the same PUSCH.

In case that contention occurs between the periodic report and theaperiodic report in the same subframe, only the aperiodic report can beperformed.

In calculating Wideband CQI/PMI, a most recently transmitted RI may beusable. RI in a PUCCH CSI report mode is independent from RI in a PUSCHCSI report mode. The RI in the PUSCH CSI report mode is valid forCQI/PMI in the corresponding PUSCH CSI report mode only.

Table 6 is provided to describe CSI feedback type transmitted on PUCCHand PUCCH CSI report mode.

TABLE 6 PMI Feedback Type No PMI (OL, TD, single-antenna) Single PMI(CL) CQI Wideband Mode 1-0 Mode 1-1 Feedback RI (only for Open-Loop SM)RI Type One Wideband CQI (4 bit) Wideband CQI (4 bit) when RI > 1, CQIof first codeword Wideband spatial CQI (3 bit) for RI > 1 Wideband PMI(4 bit) UE Mode 2-0 Mode 2-1 Selected RI (only for Open-Loop SM) RIWideband CQI (4 bit) Wideband CQI (4 bit) Best-1 CQI (4 bit) in each BPWideband spatial CQI (3 bit) for RI > 1 Best-1 indicator(L-bit label)Wideband PMI (4 bit) when RI > 1, CQI of first codeword Best-1 CQI (4bit) 1 in each BP Best-1 spatial CQI (3 bit) for RI > 1 Best-1 indicator(L-bit label)

Referring to Table 6, in the periodic report of channel information,there are 4 kinds of reporting modes (mode 1-0, mode 1-2, mode 2-0 andmode 2-1) in accordance with CQI and PMI feedback types.

CQI can be classified into Wideband (WB) CQI and Subband (SB) CQI inaccordance with CQI feedback type and PMI can be classified into No PMIor Single PMI in accordance with a presence or non-presence of PMItransmission. In Table 11, No PMI corresponds to a case of Open-Loop(OL), Transmit Diversity (TD) and single-antenna, while Single PMIcorresponds to a case of Closed-Loop (CL).

The mode 1-0 corresponds to a case that WB CQI is transmitted in theabsence of PMI transmission. In this case, RI is transmitted only incase of OL Spatial Multiplexing (SM) and one WB CQI represented as 4bits can be transmitted. If RI is greater than 1, CQI for a 1^(st)codeword can be transmitted.

The mode 1-1 corresponds to a case that a single PMI and WB CQI aretransmitted. In this case, 4-bit WB CQI and 4-bit WB PMI can betransmitted together with RI transmission. Additionally, if RI isgreater than 1, 3-bit WB spatial differential CQI can be transmitted. In2-codeword transmission, the WB spatial differential CQI may indicate adifference value between a WB CQI index for codeword 1 and a WB CQIindex for codeword 2. The difference value in-between may have a valueselected from a set {−4, −3, −2, −1, 0, 1, 2, 3} and can be representedas 3 bits.

The mode 2-0 corresponds to a case that CQI on a UE-selected band istransmitted in the absence of PMI transmission. In this case, RI istransmitted only in case of OL SM and a WB CQI represented as 4 bits maybe transmitted. A best CQI (best-1) is transmitted on each BandwidthPart (BP) and the best-1 CQI may be represented as 4 bits. And, an L-bitindicator indicating the best-1 may be transmitted together. If the RIis greater than 1, a CQI for a codeword can be transmitted.

And, the mode 2-1 corresponds to a case that a single PMI and a CQI on aUE-selected band are transmitted. In this case, together with RItransmission, 4-bit WB CQI, 3-bit WB spiral differential CQI and 4-bitWB PMI can be transmitted. Additionally, 4-bit best-1 CQI is transmittedon each BP and L-bit best-1 indicator can be transmitted together.Additionally, if RI is greater than 1, 3-bit best-1 spatial differentialCQI can be transmitted. In 2-codeword transmission, it may indicate adifference value between a best-1 CQI index of codeword 1 and a best-1CQI index of codeword 2.

For the transmission modes, periodic PUCCH CSI report modes aresupported as follows.

1) Transmission mode 1: Modes 1-0 and 2-0

2) Transmission mode 2: Modes 1-0 and 2-0

3) Transmission mode 3: Modes 1-0 and 2-0

4) Transmission mode 4: Modes 1-1 and 2-1

5) Transmission mode 5: Modes 1-1 and 2-1

6) Transmission mode 6: Modes 1-1 and 2-1

7) Transmission mode 7: Modes 1-0 and 2-0

8) Transmission mode 8: Modes 1-1 and 2-1 if a UE is set to make aPMI/RI reporting, or Modes 1-0 and 2-0 if a UE is set not to make aPMI/RI reporting

9) Transmission mode 9: Modes 1-1 and 2-1 if a UE is set to make aPMI/RI reporting and the number of CSI-RS ports is greater than 1, orModes 1-0 and 2-0 if a UE is set not to make a PMI/RI reporting and thenumber of CSI-RS port(s) is equal to 1.

The periodic PUCCH CSIU reporting mode in each serving cell is set byupper layer signaling. And, the mode 1-1 is set to either submode 1 orsubmode 2 by an upper layer signaling using a parameter‘PUCCH_format1-1_CSI_reporting_mode’.

A CQI reporting in a specific subframe of a specific serving cell in aUE-selected SB CQI means a measurement of at least one channel state ofa BP corresponding to a portion of a bandwidth of a serving cell. Anindex is given to the bandwidth part in a frequency increasing orderstarting with a lowest frequency without an increment of a bandwidth.

N_(RB) ^(DL) Indicates the number of RBs of a serving cell systembandwidth. The system bandwidth may be divided into N (1, 2, 3, . . . N)SB CQI subbands. One SB CQI may include k RBs defined in Table 15. Ifthe number of RBs of the whole bandwidth is not a multiple integer of k(┌N_(RB) ^(DL)/k┐−└N_(RB) ^(DL)/k┘>0) the number of RBs configuring alast (i.e., N^(th)) SB CQI may be determined by [Equation 4].

N _(RB) ^(DL) −k·└N _(RB) ^(DL) /k┘  [Equation 4]

Table 17 shows relationship among subband size k, BP and systembandwidth N_(RB) ^(DL).

TABLE 17 System Bandwidth Subband Size k Bandwidth Parts N_(RB) ^(DL)(RBs) (J) 6-7 NA NA  8-10 4 1 11-26 4 2 27-63 6 3  64-110 8 4

Moreover, N_(J) CQI subbands configure one bandwidth part (BP) and asystem bandwidth can be divided into J BPs. If J=1, N_(J) is equal to┌N_(RB) ^(DL)/k/J ┐. If J>1, N_(J) is equal to ┌N_(RB) ^(DL)/k/J┐ or┌N_(RB) ^(DL)/k/J┐−1. A UE calculates a CQI index for a preferred bestone (best-1) CQI band in BP and may be then able to transmit the CQIindex on PUCCH. In doing so, a best-1 indicator indicating what is thebest-1 CQI subband selected from one BP may be transmitted together. Thebest-1 indicator may be configured with L bits, where the ‘L’ can berepresented as [Equation 5].

L=┌log₂ ┌N _(RB) ^(DL) /k/J┐┐  [Equation 5]

In the above UE-selected CQI reporting mode, it is able to determine afrequency band in which a CQI index is calculated.

In the following description, a CQI transmission period is explained.

Table 8 shows CQI and PMI payload sizes of each PUCCH CSI report mode.

TABLE 8 PUCCH Reporting Modes PUCCH Mode 1-1 Mode 2-1 Mode 1-0 Mode 2-0Format Reported Mode State (bits/BP) (bits/BP) (bits/BP) (bits/BP) 1Sub-band RI = 1 NA 4 + L NA 4 + L CQI RI > 1 NA 7 + L NA 4 + L 1aSub-band 8 antenna ports RI = 1 NA 8 + L NA NA CQI/ 8 antenna ports 1 <RI < 5 NA 9 + L NA NA second 8 antenna ports RI > 4 NA 7 + L NA NA PMI 2Wideband 2 antenna ports RI = 1 6 6 NA NA CQI/PMI 4 antenna ports RI = 18 8 NA NA 2 antenna ports RI > 1 8 8 NA NA 4 antenna ports RI > 1 11 11  NA NA 2a Wideband 8 antenna ports RI < 3 NA 4 NA NA first PMI 8antenna ports 2 < RI < 8 NA 2 NA NA 8 antenna ports RI = 8 NA 0 NA NA 2bWideband 8 antenna ports RI = 1 8 8 NA NA CQI/ 8 antenna ports 1 < RI <4 11  11  NA NA second 8 antenna ports RI = 4 10  10  NA NA PMI 8antenna ports RI > 4 7 7 NA NA 2c Wideband 8 antenna ports RI = 1 8 — NANA CQI/first 8 antenna ports 1 < RI ≤ 4 11  — NA NA PMI/ 8 antenna ports4 < RI ≤ 7 9 — NA NA second 8 antenna ports RI = 8 7 — NA NA PMI 3 RI2-layer spatial 1 1 1 1 multiplexing 4-layer spatial 2 2 2 2multiplexing 8-layer spatial 3 3 NA NA multiplexing 4 Wideband RI = 1 orRI > 1 NA NA 4 4 CQI 5 RI/first 8 antenna ports, 2- 4 NA NA NA PMI layerspatial multiplexing 8 antenna ports, 4 and 5 8-layer spatialmultiplexing 6 RI/PTI 8 antenna ports, 2- NA 2 NA NA layer spatialmultiplexing 8 antenna ports, 4- NA 3 NA NA layer spatial multiplexing 8antenna ports, 8- NA 4 NA NA layer spatial multiplexing

Referring to Table 8, each CQI/PMI and RI reporting type (PUCCHreporting type) supported for PUCCH CSI report mode can be described asfollows.

Reporting Type 1 supports CQI feedback for a subband selected by a UE.

Reporting Type 1a supports subband CQI and 2^(nd) PMI feedback.

Reporting Type 2/2b/2c supports WB CQI and PMI feedback.

Reporting Type 2a supports WB PMI feedback.

Reporting Type 3 supports RI feedback.

Reporting Type 4 supports WB CQI.

Reporting Type 5 supports RI and WB PMI feedback.

Reporting Type 6 supports RI and PTI feedback.

A UE can receive information including a combination of a transmissionperiod of channel information and an offset from an upper layer by RRCsignaling. The UE can transmit the channel information to a base stationbased on the provided information on the channel informationtransmission period. In each serving cell, a period N_(pd) in a subframefor a CQI/PMI reporting and an offset N_(OFFSET,CQI) in the subframe aredetermined based on a parameter ‘cqi-pmi-ConfigIndex’ (I_(CQI/PMI)) setup by upper layer signaling [cf. Table 14 and Table 15]. An offsetN_(OFFSET,RI) related to a period M_(RI) for an RI reporting isdetermined based on a parameter ‘ri-ConfigIndex’ (I_(RI)) [cf. Table16]. The offset NOFFSET,RI for the RI reporting has a value of {0, −1 .. . −(N_(pd)−1)} In case that a UE is set to report abnormality of oneCSI subframe set, the ‘cqi-pmi-ConfigIndex’ and the ‘ri-ConfigIndex’correspond to the period and offset of CQI/PMI and RI for a subframe set1, respectively. And, the ‘cqi-pmi-ConfigIndex2’ and the‘ri-ConfigIndex2’ correspond to the period and offset of CQI/PMI and RIfor a subframe set 2, respectively.

Table 9 shows the mapping relation between N_(pd) and N_(OFFSET,CQI) ofa parameter ICQI/PMI in FDD.

TABLE 9 I_(CQI/PMI) Value of N_(pd) Value of N_(OFFSET,CQI)  0 ≤I_(CQI/PMI) ≤ 1 2 I_(CQI/PMI)  2 ≤ I_(CQI/PMI) ≤ 6 5 I_(CQI/PMI)-2  7 ≤I_(CQI/PMI) ≤ 16 10 I_(CQI/PMI)-7  17 ≤ I_(CQI/PMI) ≤ 36 20I_(CQI/PMI)-17  37 ≤ I_(CQI/PMI) ≤ 76 40 I_(CQI/PMI)-37  77 ≤I_(CQI/PMI) ≤ 156 80 I_(CQI/PMI)-77 157 ≤ I_(CQI/PMI) ≤ 316 160I_(CQI/PMI)-157 I_(CQI/PMI) = 317 Reserved 318 ≤ I_(CQI/PMI) ≤ 349 32I_(CQI/PMI)-318 350 ≤ I_(CQI/PMI) ≤ 413 64 I_(CQI/PMI)-350 414 ≤I_(CQI/PMI) ≤ 541 128 I_(CQI/PMI)-414 542 ≤ I_(CQI/PMI) ≤ 1023 Reserved

Table 10 shows the mapping relation between N_(pd) and N_(OFFSET,CQI) ofa parameter ICQI/PMI in TDD.

TABLE 10 I_(CQI/PMI) Value of N_(pd) Value of N_(OFFSET, CQI)I_(CQI/PMI) = 0 1 I_(CQI/PMI) 1 ≤ I_(CQI/PMI) ≤ 5 5 I_(CQI/PMI) − 1   6≤ I_(CQI/PMI) ≤ 15 10 I_(CQI/PMI) − 6  16 ≤ I_(CQI/PMI) ≤ 35 20I_(CQI/PMI) − 16 36 ≤ I_(CQI/PMI) ≤ 75 40 I_(CQI/PMI) − 36  76 ≤I_(CQI/PMI) ≤ 155 80 I_(CQI/PMI) − 76 156 ≤ I_(CQI/PMI) ≤ 315 160 I_(CQI/PMI) − 156  316 ≤ I_(CQI/PMI) ≤ 1023 Reserved

Table 11 shows the mapping relation between M_(RI) and N_(OFFSET,RI) ofa parameter I_(RI) in TDD.

TABLE 11 I_(RI) Value of M_(RI) Value of N_(OFFSET, RI)  0 ≤ I_(RI) ≤160 1 −I_(RI) 161 ≤ I_(RI) ≤ 321 2 −(I_(RI) − 161) 322 ≤ I_(RI) ≤ 482 4−(I_(RI) − 322) 483 ≤ I_(RI) ≤ 643 8 −(I_(RI) − 483) 644 ≤ I_(RI) ≤ 80416 −(I_(RI) − 644) 805 ≤ I_(RI) ≤ 965 32 −(I_(RI) − 805)  966 ≤ I_(RI) ≤1023 Reserved

2.7 Restricted CSI Measurement

To mitigate the effect of interference between cells in a wirelessnetwork, network entities may cooperate with each other. For example,other cells except a cell A transmit only common control informationwithout transmitting data during the duration of a specific subframe forwhich the cell A transmits data, whereby interference with a userreceiving data in the cell A may be minimized.

In this way, interference between cells may be mitigated by transmittingonly minimal common control information from other cells except a celltransmitting data at a specific time through cooperation between cellsin a network.

For this purpose, if a higher layer configures two CSI measurementsubframe sets CCSI,0 and CCSI,1, a UE may perform Resource-RestrictedMeasurement (RRM). At this time, it is assumed that CSI referenceresources corresponding to the two measurement subframe sets belong toonly one of the two subframe sets.

The following Table 12 illustrates an example of a higher-layer signalthat configures CSI subframe sets.

TABLE 12 CQI-ReportConfig-r10 ::= SEQUENCE {   cqi-ReportAperiodic-r10CQI-ReportAperiodic-r10 OPTIONAL,  -- Need ON   nomPDSCH-RS-EPRE-OffsetINTEGER (−1..6),   cqi-ReportPeriodic-r10 CQI-ReportPeriodic-r10OPTIONAL,  -- Need ON   pmi-RI-Report-r9 ENUMERATED {setup}OPTIONAL,  -- Cond PMIRIPCell   csi-SubframePatternConfig-r10 CHOICE {   release NULL,    setup SEQUENCE {      csi-MeasSubframeSet1-r10MeasSubframePattern-r10,      csi-MeasSubframeSet2-r10MeasSubframePattern-r10    }   } OPTIONAL -- Need ON }

Table 12 illustrates an example of CQI report configuration (CQI-ReportConfig) message transmitted to configure CSI subframe sets. TheCQI-Report configuration message may include an aperiodic CQI reportcqi-ReportAperiodic-r10 Information Element (IE), anomPDSCH-RS-EPRE-Offset IE, a periodic CQI report cqi-ReportPeriodic-r10IE, a PMI-RI report pmi-RI-Report-r9 IE, and a CSI subframe patternconfiguration csi-subframePatternConfig IE. At this time, the CSIsubframe pattern configuration IE includes CSI measurement subframe set1 information csi-MeasSubframeSet1 IE and a CSI measurement subframe set2 information csi-MeasSubframeSet2 IE, which indicate measurementsubframe patterns for the respective subframe sets.

In this case, each of the csi-MeasSubframeSet1-r10 IE and thecsi-MeasSubframeSet2-r10 IE is 40-bit bitmap information representinginformation on subframes belonging to each subframe set. Also, aperiodicCQI report CQI-ReportAperiodic-r10 IE is used to configure an aperiodicCQI report for the UE, and the periodic CQI reportCQI-ReportPeriodic-r10 is used to configure a periodic CQI report forthe UE.

The nomPDSCH-RS-EPRE-Offset IE indicates a value of Δ_(offset). At thistime, an actual value is set to Δ_(offset) value*2 [dB]. Also, thePMI-RI report IE indicates configuration or non-configuration of aPMI/RI report. Only when a transmission mode is set to TM8, TM9, orTM10, the E-UTRAN configures the PMI-RI Report IE.

3. LTE-U System

3.1 LTE-U System Configuration

Hereinafter, methods for transmitting and receiving data in a carrieraggregation environment of an LTE-A band corresponding to a licensedband and an unlicensed band will be described. In the embodiments of thepresent invention, an LTE-U system means an LTE system that supportssuch a CA status of a licensed band and an unlicensed band. A WiFi bandor Bluetooth (BT) band may be used as the unlicensed band.

FIG. 12 illustrates an example of a CA environment supported in an LTE-Usystem.

Hereinafter, for convenience of description, it is assumed that a UE isconfigured to perform wireless communication in each of a licensed bandand an unlicensed band by using two component carriers (CCs). Themethods which will be described hereinafter may be applied to even acase where three or more CCs are configured for a UE.

In the embodiments of the present invention, it is assumed that acarrier of the licensed band may be a primary CC (PCC or Pcell), and acarrier of the unlicensed band may be a secondary CC (SCC or Scell).However, the embodiments of the present invention may be applied to evena case where a plurality of licensed bands and a plurality of unlicensedbands are used in a carrier aggregation method. Also, the methodssuggested in the present invention may be applied to even a 3GPP LTEsystem and another system.

In FIG. 12, one eNB supports both a licensed band and an unlicensedband. That is, the UE may transmit and receive control information anddata through the PCC which is a licensed band, and may also transmit andreceive control information and data through the SCC which is anunlicensed band. However, the status shown in FIG. 12 is only example,and the embodiments of the present invention may be applied to even a CAenvironment that one UE accesses a plurality of eNBs.

For example, the UE may configure a macro eNB (M-eNB) and a Pcell, andmay configure a small eNB (S-eNB) and an Scell. At this time, the macroeNB and the small eNB may be connected with each other through abackhaul network.

In the embodiments of the present invention, the unlicensed band may beoperated in a contention-based random access method. At this time, theeNB that supports the unlicensed band may perform a carrier sensing (CS)procedure prior to data transmission and reception. The CS proceduredetermines whether a corresponding band is reserved by another entity.

For example, the eNB of the Scell checks whether a current channel isbusy or idle. If it is determined that the corresponding band is idlestate, the eNB may transmit a scheduling grant to the UE to allocate aresource through (E)PDCCH of the Pcell in case of a cross carrierscheduling mode and through PDCCH of the Scell in case of aself-scheduling mode, and may try data transmission and reception.

At this time, the eNB may configure a transmission opportunity (TxOP)duration comprised of N consecutive subframes. In this case, a value ofN and a use of the N subframes may previously be notified from the eNBto the UE through higher layer signaling through the Pcell or through aphysical control channel or physical data channel.

3. 2 TxOP Duration

An eNB may transmit and receive data to and from one UE for a TxOPduration, and may configure a TxOP duration comprised of N consecutivesubframes for each of a plurality of UEs and transmit and receive datain accordance with TDM or FDM. At this time, the eNB may transmit andreceive data through a Pcell which is a licensed band and an Scell whichis an unlicensed band for the TxOP duration.

However, if the eNB transmits data in accordance with a subframeboundary of an LTE-A system corresponding to a licensed band, a timinggap may exist between an idle determination timing of the Scell which isan unlicensed band and an actual data transmission timing. Particularly,since the Scell should be used as an unlicensed band, which cannot beused exclusively by a corresponding eNB and a corresponding UE, throughCS based contention, another system may try information transmission forthe timing gap.

Therefore, the eNB may transmit a reservation signal from the Scell toprevent another system from trying information transmission for thetiming gap. In this case, the reservation signal means a kind of “dummyinformation” or “a copy of a part of PDSCH” transmitted to reserve acorresponding resource region of the Scell as a resource of the eNB. Thereservation signal may be transmitted for the timing gap (i.e., from theidle determination timing of the Scell to the actual transmissiontiming).

3.3 Method for Configuring TxOP Duration

FIG. 13 illustrates one of methods for configuring a TxOP duration.

An eNB may previously configure a TxOP duration semi-statically througha Pcell. For example, the eNB may transmit a value of N corresponding tothe number of subframes constituting the TxOP duration and configurationinformation on a use of the corresponding TxOP duration to a UE througha higher layer signal (for example, RRC signal) (S1310).

However, the step S1310 may be performed dynamically in accordance withsystem configuration. In this case, the eNB may transmit configurationinformation on the TxOP duration to the UE through a PDCCH or E-PDCCH.

The Scell may perform a carrier sensing (CS) procedure to check whethera current channel state is an idle state or a busy state (S1320).

The Pcell and the Scell may be managed by their respective eNBsdifferent from each other or the same eNB. However, if the Pcell and theScell are managed by different base stations, information on a channelstate of the Scell may be delivered to the Pcell through a backhaul(S1330).

Afterwards, at a subframe configured as the TxOP duration, the UE maytransmit and receive data through the Pcell and the Scell. If the use ofthe corresponding TxOP is configured for downlink data transmission atthe step S1310, the UE may receive DL data through the Scell for theTxOP duration, and if the use of the corresponding TxOP is configuredfor uplink data transmission at the step S1310, the UE may transmit ULdata through the Scell (S1340).

4. Method for Measuring and Reporting Interference

4.1 Interference Measurement at TxOP Duration

An eNB should know CSI (e.g., CQI, RI, PMI) with a UE, which willreceive DL data, to transmit downlink data by efficiently using aresource of an Scell. In the LTE/LTE-A system, the eNB transmits variouskinds of reference signals (e.g., CRS, DM-RS, CSI-RS, CSI-IM). At thistime, the CRS is transmitted every subframe (SF), the DM-RS istransmitted from RB for transmitting DL data, and the CSI-RS and theCSI-IM are transmitted at a predefined period (e.g., 5 ms, 10 ms, etc.).

The UE performs signal measurement (SM) and interference measurement(IM) through the reference signal and calculates proper CSI (e.g., CQI,RI, PMI) on the basis of the measured result. Also, the UE reports theCSI to the eNB periodically or aperiodically. The eNB which has receivedperiodic or aperiodic CSI report may configure a proper MCS level on thebasis of the CSI for a UE which will receive DL data, and may transmitthe DL data in accordance with the corresponding MCS level.

At this time, in case of the LTE-A system operated in a licensed band,if CSI-IM is configured through cooperative transmission betweenneighboring eNBs, the UEs may measure desired interference on the basisof the configured CSI-IM. However, in case of an unlicensed band (forexample, TxOP duration of Scell), since the UE is operated in acontention based random access mode, even though CSI-IM is configuredperiodically, it is not certain that data of the eNB will be transmittedat SF at which the CSI-IM will be transmitted. Also, even though DL dataare transmitted, unexpected interference may occur due to a hidden nodeproblem that another eNB or system which is not checked by CS at thecorresponding subframe transmits data. Therefore, to solve this, thepresent invention suggests a method for defining valid CSI-IM andconfiguring CSI-IM and an effective interference averaging method.

4.2 Method for Configuring CSI-IM in Scell

In the embodiments of the present invention, the eNB may configure andmanage the TxOP duration described in section 3. That is, the eNB mayperform scheduling for the Pcell of the licensed band and the Scell ofthe unlicensed band. If the eNB of the Pcell and the eNB of the Scellare different from each other, the two eNBs may be operated incooperation with each other by using the Pcell and the Scell.

4.2.1 Method 1 for Configuring CSI-IM

As one embodiment of the present invention, CSI-IM is configured inaccordance with a configuration period defined in the LTE/LTE-A system,and it may be defined that only CSI-IM corresponding to the TxOPduration is valid.

FIG. 14 illustrates one of methods for configuring CSI-IM transmittedfrom an Scell.

An Scell operated in an unlicensed band is shown in FIG. 14, and it isassumed that a size N of the TxOP duration corresponds to 6 SFs.Referring to FIG. 14, the eNB determines whether a corresponding cell isan idle state by performing carrier sensing (CS) at a subframe index M−1(i.e., SF #M−1) of the Scell, and transmits a reservation signal untilnext SF #M if the corresponding cell is an idle state. Also, the eNBtransmits DL data to the UE continuously for 6 SFs corresponding to thesize of the TxOP duration, which is previously configured through theScell.

At this time, it is assumed that a starting point SF #M of the TxOPduration is designated through previously defined signaling (forexample, higher layer signaling or physical control/data channel). Also,it may previously be defined that a period of CSI-IM is 5 ms and isconfigured at SF #M+1 and SF #M+6. At this time, since the eNB has triedDL data transmission at SF #M+1, a neighboring eNB or another system(i.e., non-LTE system), which may sense DL data transmission, does nottry DL data transmission at the corresponding SF. On the other hand,since the eNB does not transmit DL data at SF #M+6, another system(i.e., non-LTE system) may determine an idle state and then try datatransmission at the corresponding SF in view of operation features ofthe unlicensed band.

Therefore, if the UE performs IM through CSI-IM within SF (e.g., SF#M+6) which does not belong to the TxOP duration, the UE may obtain awrong IM result. Therefore, in the embodiments of the present invention,it is preferable that only CSI-IM within the TxOP duration is defined asvalid CSI-IM and the UE performs IM through the CSI-IM.

In the embodiments of the present invention, higher layer signaling maymean RRC signal, MAC signal, etc., a physical channel means a PDCCH, anda physical data channel means a PDSCH. At this time, E-PDCCH may betransmitted to the physical data channel.

4.2.2 Method 2 for Configuring CSI-IM

As another embodiment of the present invention, a position of CSI-IM maybe configured based on a previously configured period (for example,through higher layer signaling or physical control/data channel) or SFoffset from a starting point of TxOP.

FIG. 15 illustrates another one of methods for configuring CSI-IMtransmitted from an Scell.

The eNB may be configured to configure CSI-IM of at least two or moretimes within the TxOP duration by configuring a period P of CSI-IMconfigured in the Scell semi-statically to be smaller than the number Nof SFs included within the TxOP duration (P<N).

For example, in FIG. 15, it is assumed that a period of CSI-IMcorresponds to 4 SFs and SF offset for indicating a subframe at whichCSI-IM is configured is set to 1. In this case, the eNB may configureCSI-IM at SF #M+1 after 1 SF and SF #M+5 after 4 SFs based on thestarting point of TxOP. Therefore, although the number of valid CSI-IMsis 1 in FIG. 15, since the number of valid CSI-IMs is 2 in FIG. 15, theeNB may increase the number of valid CSI-IMs by configuring CSI-IMsemi-statically in accordance with the TxOP duration occurringirregularly. Therefore, the UE may obtain the more exact IM result.

4.2.3 Method 3 for Configuring CSI-IM

If the Scell of the unlicensed band is used for data offloading of thePcell, the actual TxOP duration may occur irregularly (i.e., aperiodic).Therefore, if the eNB periodically configures a CSI-IM resource like theLTE-A system (i.e., Rel-11) (e.g., CSI-IM configuration of 5 ms), thenumber of valid CSI-IMs may be reduced in case of the method describedin section 4.3.1. To solve this, the TxOP duration on the Scell may beconfigured periodically, whereby CSI-IM resource may be configuredefficiently. That is, if the eNB properly configures a period of theTxOP and a size of the TxOP duration in accordance with a configurationperiod of the CSI-IM resource, the number of valid CSI-IMs may beincreased.

In the embodiments of the present invention, a configuration period ofthe CSI-IM resource may be defined as ‘P’, a period of the TxOP durationmay be defined as ‘K’, and the size of the TxOP duration may be definedas ‘N’. At this time, if the eNB is configured to have a value of K=2Pand a size of N=P+1, the number of valid SFs at which CSI-IM resource isconfigured may be assured of at least 2 or more within one TxOP period.

At this time, the period ‘K’ of the TxOP duration, the configurationperiod ‘P’ of the CSI-IM resource, and the size ‘N’ of the TxOP durationmay be notified from the eNB to the UE through a higher layer signal(e.g., RRC signal) or physical control/data channel.

FIG. 16 illustrates still another one of methods for configuring CSI-IMtransmitted from an Scell.

Referring to FIG. 16, since a period ‘P’ of the CSI-IM is set to 5 ms,the CSI-IM resource may be allocated to SF #M, M+5, M+10, M+15. Also, itis assumed that the period ‘K’ of the TxOP duration corresponds to 10SFs and the size ‘N’ of one TxOP duration is set to 6 SFs. At this time,since all of the configured CSI-IMs exist within the TxOP duration, allCSI-IMs are valid. That is, the period of the TxOP and the TxOP durationare configured properly in accordance with the configuration period ofthe allocated CSI-IM resource, whereby the number of valid CSI-IMs maybe increased.

FIG. 17 illustrates further still another one of methods for configuringCSI-IM transmitted from an Scell.

The eNB may fail to start the TxOP duration from a desired SF due to achannel state in view of features of an unlicensed band operation. Forexample, although the TxOP duration is tried to start from SF #M+10 asshown in FIG. 17, if it is determined that a busy state is continuouslymaintained as a result of CS, actual TxOP starting SF may be delayed asmuch as 1 SF or more. In this case, the eNB may notify the UE that thestarting point of the TxOP duration has been delayed at SF #M+10,through PDCCH or E-PDCCH of the Pcell, and may notify the UE how manySFs have been delayed at the actual TxOP starting point.

Since 1 SF has been delayed in FIG. 17, at SF #M+11, the eNB may notifythe UE of the delay through (E)PDCCH of the Pcell, and the Scell may beconfigured to give 1 SF offset at the CSI-IM resource position. That is,since the TxOP starting point has been delayed as much as 1 SF, CSI-IMmay be configured at SF #M+11, M+16 delayed as much as 1 SF, whereby thenumber of valid CSI-IMs may be increased.

4.3 Method for Averaging Interference

4.3.1 CSI-IM Measurement Duration Configuration

For a window size for averaging interference measured from valid CSI-IM,the eNB may configure a CSI-IM duration. At this time, the CSI-IMduration indicating a window size may be configured by 1) timecorresponding to several msec, 2) one TxOP duration, or 3) a pluralityof TxOP durations.

At this time, a CSI-IM duration value may previously be notified fromthe eNB to the UE through a higher layer signal (via PCell) or physicalcontrol/data channel. For example, if the CSI-IM duration value is 1TxOP duration, the eNB and/or the UE initiates an interference averagingvalue every TxOP duration. If the CSI-IM duration corresponds to 6 TxOPdurations, the UE may measure interference by using all of CSI-IMresources on the 6 TxOP durations. In the embodiments of the presentinvention, this will be referred to as interference averaging.

The CSI-IM duration for interference averaging may be configured basedon SF at which a current TxOP duration ends. For example, if theconfigured CSI-IM duration is 20 ms duration, the UE may performinterference averaging by using all of valid CSI-IM resources for 20 msbased on SF #M+5 at which the current TxOP duration ends in FIG. 19. Atthis time, valid CSI-IM may be defined by the method suggested in thesection 4.2.1. FIG. 19 illustrates an example of TxOP subframeconfiguration when a duration value for interference averaging is set.

In another aspect of the present invention, if it is determined thatreliable CSI measurement is not performed as there is no valid CSI-IMresource for the configured CSI-IM duration or there are a small numberof valid CSI-IMs, the eNB may feed a CSI (e.g., CQI/RI/PMI) valuecorresponding to a previously defined initial value back through ahigher layer signal or physical control/data channel. At this time, asan example of the initial value, CQI value may be set to ‘Out of Range’value.

4.3.2 Method for Using Long-Term Channel Statistics

In view of features of unlicensed band operation, another system (e.g.,non-LTE system) may try data transmission even for a TxOP duration dueto a hidden node problem. For example, even though the UE belongs to theTxOP duration like SF #M+1 in FIG. 14, the UE may measure too highinterference due to data transmission of another system, which is causedby a hidden node problem.

For example, it is assumed that the eNB configures a CSI-IM duration asone TxOP duration in section 4.3.1. At this time, the UE may measure toohigh interference due to a hidden node problem at the corresponding TxOPduration and calculate a CQI value based on the measured interference tofeed the calculated CQI value back. In this case, the UE may beallocated with an MCS level too lower than a normal state. Therefore, DLdata transmission for the UE may be managed very inefficiently.

That is, if the UE reports CSI (e.g., CQI, etc.) to the eNB by usingonly a simple averaging value of measured interference, a too low MCSlevel may be allocated by interference caused by a hidden node problem.To solve this, the UE may be configured to use long-term channelstatistics for an interference measurement value.

At this time, as an example of statistics, a variance value as well asan interference average value may be used.

As another example of statistics, a cumulative distribution function(CDF) distribution of an interference value may be used. For example,the UE may select MCS having a block error rate (BLER) of 10% in aninterference status of a high x % as CQI and report the correspondingCQI to the eNB.

That is, the UE may report, to the eNB, CQI of a condition or morepreviously configured based on an average value, variance value and/orCDF distribution of interference with respect to the interference valuemeasured based on the CSI-IM duration for interference averaging.

FIG. 19 illustrates an example of CDF distribution for interferenceaveraging.

The UE may store CDF distribution of FIG. 19 based on a histogram of ameasured interference value. At this time, an interference status ofhigh x % in FIG. 19 means that an interference value measured by the UEis −60 dBm or less. Therefore, the UE may perform interference averagingexcept interference values exceeding −60 dBm. The UE may select MCShaving a block error rate (BLER) of 10% as CQI based on interferenceaverage values obtained through this interference averaging and reportthe corresponding CQI to the eNB.

4.3.3 Method for Averaging Interference Using Two Interference AveragingValues

As another method for solving interference averaging distortion due to ahidden node problem on a TxOP duration, the UE may configure twointerference averaging values based on a specific threshold value. Forexample, one may be a first interference average (i.e., Type A average)for a whole CSI-IM duration, and the other one may be a secondinterference average (i.e., Type B average) except interferencedetermined to be too high.

In this case, if interference measured for a random CSI-IM duration ishigher than the first interference average value as much as a thresholdvalue or more, the UE may exclude the corresponding interference fromthe second interference average value. At this time, the threshold valuemay previously be notified from the eNB to the UE through a higher layersignal or physical control/data channel.

Therefore, the UE may calculate two CQI values through two IM values(i.e., Type A average value and Type B average value). For example, theCQI value calculated based on the first interference average by the UEmay be defined as a first CQI value (i.e., Type A CQI), and the CQIvalue calculated based on the second interference average (i.e., Type Baverage) by the UE may be defined as a second CQI value (i.e., Type BCQI).

At this time, the first CQI value may be construed as a conservative CQIvalue considering interference of another system due to a hidden nodeproblem, and the second CQI value may be construed as an aggressive CQIvalue in an ideal environment having no interference from anothersystem.

In this case, the UE may report only one representative CQI value of thetwo CQI values (e.g., first and second CQI values) to the eNB. Also, theUE may report an index for the corresponding CQI value to indicate whichCQI value is reported, during CQI report.

Otherwise, the UE may select one of the two CQI values based on thelong-term channel statistics described in the section 4.3.2 and reportonly the selected CQI to the eNB.

Otherwise, the UE may report the two CQI values to the eNB. At thistime, which one of the two CQI values which are fed back will beselected or how the two CQI values will be used properly may bedetermined by the eNB. If the UE notifies the eNB of both the two CQIvalues, the UE may report a differential value (or offset value) of thetwo CQI values to the eNB. For example, the UE may report one of thefirst CQI value and the second CQI value and additionally report adifferential value of the two CQI values to reduce signaling overhead.

4.3.4 Method for Interworking Aperiodic CSI Triggering

The UE may regard that a valid CSI-IM resource previously defined (orsignaled) exists on a CSI reference resource only interworking withaperiodic CSI triggering for the Scell. In other words, the UE mayassume that a CSI-IM resource which is not interworking with aperiodicCSI triggering does not exist. In this case, the UE may measureinterference by using the valid CSI-IM only on the CSI referenceresource interworking with aperiodic CSI triggering.

In order that the UE should know an exact position of the valid CSI-IMin the sections 4.3.1 to 4.3.3, the UE should explicitly know when theTxOP duration starts and when the TxOP duration ends. That is, it ispreferable that the eNB notifies UEs, which perform CSI measurement,other than a UE which is scheduled a PDSCH for the TxOP duration, of theTxOP duration (for example, through a common search space (CSS)).

However, notification of the TxOP duration to other UEs other than theUE, which actually receives a PDSCH every TxOP duration, through the CSSmay be high overhead in view of the eNB. Therefore, instead of notifyingall UEs of a starting point and an end point of the TxOP duration, theeNB may notify whether a PDSCH is actually scheduled at SFs at which theTxOP duration is allocated, through DCI in the same manner as the legacyLTE/LTE-A system. That is, although the UE does not know the startingpoint and the end point of the TxOP duration explicitly, the UE may beoperated to receive the PDSCH if there is DCI at the corresponding SFand so as not to receive the PDSCH if there is no DCI at thecorresponding SF.

As described above, if the UE does not know the starting point and theend point of the TxOP, each UE may have a difficulty in finding thevalid CSI-IM resource. At this time, it may be assumed that CSI-IM isvalid at only SF interworking with aperiodic CSI triggering.

FIG. 20 illustrates one of methods for configuring CSI-IM interworkingwith aperiodic CSI triggering.

In FIG. 20, assuming that a triggering timing point of aperiodic CSI isSF #M, SF interworking with aperiodic CSI triggering may be SF #M or SF#(M−k). At this time, CSI-IM interworking with aperiodic CSI triggeringmeans that CSI-IM is configured at SF #M or SF #(M−k) prior to k SF ifaperiodic CSI is triggered at the same SF #M through a PDCCH. The valueof k is a value previously set through a higher layer signal or physicalcontrol/data channel between the eNB and the UE.

The UE is characterized to perform interference averaging for only SFinterworking with aperiodic CSI triggering, and may perform interferencemeasurement through other physical signal (for example, cell-specificreference signal, UE-specific reference signal, CSI-RS, etc.) inaddition to CSI-IM of the corresponding SF.

4.3.5 RRM Measurement and Report

The UE may perform radio resource management (RRM) measurement for theScell and report the RRM measurement value to the eNB.

For example, the RRM measurement value may be a reference signalreceived quality (RSRQ) value within the TxOP duration or theinterference averaging value described in the sections 4.3.1 to 4.3.4.Alternatively, the RRM measurement value may be a new metric value notthe RSRQ value or the interference averaging value. For example, thereis {RSRP}/{Average interference} value as an average interference valuefor taking an average within the TxOP duration only. The RSRP value is areceived power value of a reference signal transmitted from the eNB, andcorresponds to a cell power value.

If the eNB which has received the RRM measurement value determines thatinterference of a specific UE is serious on the TxOP duration, the eNBmay not try data transmission to the corresponding UE through the Scell.At this time, whether interference is serious or not may be determinedby {RRM measurement value}>{previously defined (or signaled) thresholdvalue}.

4.3.6 Extensive Application at CSI-RS Resource

The aforementioned embodiments of the present invention may equally beapplied to even a case that CSI-RS resource is configured as well as acase that CSI-IM resource is configured.

4.4 Method for Measuring Interference Using CSI-IM and AveragingInterference

Hereinafter, methods for performing IM in a UE by using CSI-IM,measuring CSI by using IM, and reporting the measured CSI to an eNB willbe described based on the aforementioned embodiments of the presentinvention.

FIG. 21 illustrates one of methods for configuring CSI-IM in an eNB andreporting CSI from a UE by using the configured CSI-IM.

The eNB may configure CSI-IM configuration information. The CSI-IMconfiguration information may include one or more of a configurationperiod value ‘P’ of the CSI-IM resource, a period value ‘K’ of the TxOPduration, and a size ‘N’ of the TxOP duration (S2110).

The eNB may transmit the CSI-IM configuration information to the UEsemi-statically by using a higher layer signal (e.g., RRC or MAC signal)through the Pcell. That is, the UE may use the CSI-IM resource inaccordance with the CSI-IM configuration information for the TxOPduration (S2120).

Afterwards, if DL data should be transmitted through the Scell, the eNBmay perform a carrier sensing (CS) procedure to determine whether acurrent channel state is a busy state or an idle state (S2130).

If the channel state is an idle state, the eNB may transmit DL data forthe TxOP duration comprised of ‘N’ number of subframes through the Scell(S2140).

The UE may measure CSI by using the CSI-IM configuration informationreceived at the step S2120. For example, the UE may identify SFs atwhich the CSI-IM resource is configured, based on the CSI-IMconfiguration information, and may measure interference on the TxOPduration at the corresponding SFs on the basis of the CSI-IM resource.Also, the UE may measure CSI on the TxOP duration based on the measuredinterference and DL data and/or reference signals transmitted for theTxOP duration (S2150).

The UE may report the measured CSI to the eNB periodically oraperiodically. The periodic or aperiodic CSI report method may beperformed based on the methods described in the section 2.6 (S2160).

In another aspect of the present invention, at the step S2120, the eNBmay transmit the CSI-IM configuration information to the UE dynamicallythrough a physical layer signal (for example, PDCCH or PDSCH). In thiscase, if the TxOP duration is configured aperiodically in the Scell ofthe unlicensed band, the CSI-IM resource may be configured moreadaptively although signaling overhead may be more increased than thecase that the CSI-IM configuration information is transmittedsemi-statically.

The embodiment described in FIG. 21 may be applied to the methodsdescribed in the aforementioned sections 4.1 and 4.2. For example, thesections 4.2.1 to 4.2.3 may be applied to the method for configuringCSI-IM configuration information in the eNB.

FIG. 22 illustrates a method for calculating CSI by means of a UE on thebasis of CSI-IM duration information. FIG. 22 is provided to describethe step S2150 in more detail.

The eNB may transmit CSI-IM duration information to the UE by using ahigher layer signal (for example, RRC or MAC signal) or a physical layerchannel to configure CSI-IM (S2210).

The UE performs interference measurement by using CSI-IM correspondingto the TxOP duration on the basis of the CSI-IM duration information(S2220).

Also, the UE may perform interference averaging to prevent distortion ofinterference due to a hidden node problem from occurring. At this time,the methods for averaging interference as described in the sections4.3.1 to 4.3.4 based on the interference measured at the step S2220 maybe used as the method for averaging interference (S2230).

The UE may calculate CSI on the TxOP duration based on the measuredinterference value, received DL data and CSI-RS and report thecalculated CSI to the eNB (S2240, S2250).

5. Apparatus

Apparatuses illustrated in FIG. 23 are means that can implement themethods described before with reference to FIGS. 1 to 22.

A UE may act as a transmitter on a UL and as a receiver on a DL. An eNBmay act as a receiver on a UL and as a transmitter on a DL.

That is, each of the UE and the eNB may include a transmitter 2340 or2350 and a receiver 2360 or 2370, for controlling transmission andreception of information, data, and/or messages, and an antenna 2300 or2310 for transmitting and receiving information, data, and/or messages.

Each of the UE and the eNB may further include a processor 2320 or 2330for implementing the afore-described embodiments of the presentdisclosure and a memory 2380 or 2390 for temporarily or permanentlystoring operations of the processor 2320 or 2330.

The embodiments of the present invention may be performed using theaforementioned components and functions of the UE and eNB. For example,the processor of the eNB may configure a TxOP duration and transmitconfiguration information on the TxOP duration to the UE by combinationof the methods disclosed in the aforementioned sections 1 to 4. Also,the processor of the eNB may control the transmitter and receiver tosupport the operation of the TxOP duration. The processor of the UE maysupport the operation of the TxOP duration on the basis of theconfiguration information on the TxOP duration, which is received fromthe eNB. At this time, the processor of the UE may support the TxOPoperation by controlling the transmitter and the receiver. The detailedoperation will be understood with reference to the section 3 and thesection 4.

The transmitter and the receiver of the UE and the eNB may perform apacket modulation/demodulation function for data transmission, ahigh-speed packet channel coding function, OFDMA packet scheduling, TDDpacket scheduling, and/or channelization. Each of the UE and the eNB ofFIG. 23 may further include a low-power Radio Frequency(RF)/Intermediate Frequency (IF) module.

Meanwhile, the UE may be any of a Personal Digital Assistant (PDA), acellular phone, a Personal Communication Service (PCS) phone, a GlobalSystem for Mobile (GSM) phone, a Wideband Code Division Multiple Access(WCDMA) phone, a Mobile Broadband System (MBS) phone, a hand-held PC, alaptop PC, a smart phone, a Multi Mode-Multi Band (MM-MB) terminal, etc.

The smart phone is a terminal taking the advantages of both a mobilephone and a PDA. It incorporates the functions of a PDA, that is,scheduling and data communications such as fax transmission andreception and Internet connection into a mobile phone. The MB-MINIterminal refers to a terminal which has a multi-modem chip built thereinand which can operate in any of a mobile Internet system and othermobile communication systems (e.g. CDMA 2000, WCDMA, etc.).

Embodiments of the present disclosure may be achieved by various means,for example, hardware, firmware, software, or a combination thereof.

In a hardware configuration, the methods according to exemplaryembodiments of the present disclosure may be achieved by one or moreApplication Specific Integrated Circuits (ASICs), Digital SignalProcessors (DSPs), Digital Signal Processing Devices (DSPDs),Programmable Logic Devices (PLDs), Field Programmable Gate Arrays(FPGAs), processors, controllers, microcontrollers, microprocessors,etc.

In a firmware or software configuration, the methods according to theembodiments of the present disclosure may be implemented in the form ofa module, a procedure, a function, etc. performing the above-describedfunctions or operations. A software code may be stored in the memory2380 or 2390 and executed by the processor 2320 or 2330. The memory islocated at the interior or exterior of the processor and may transmitand receive data to and from the processor via various known means.

Those skilled in the art will appreciate that the present disclosure maybe carried out in other specific ways than those set forth hereinwithout departing from the spirit and essential characteristics of thepresent disclosure. The above embodiments are therefore to be construedin all aspects as illustrative and not restrictive. The scope of theinvention should be determined by the appended claims and their legalequivalents, not by the above description, and all changes coming withinthe meaning and equivalency range of the appended claims are intended tobe embraced therein. It is obvious to those skilled in the art thatclaims that are not explicitly cited in each other in the appendedclaims may be presented in combination as an embodiment of the presentdisclosure or included as a new claim by a subsequent amendment afterthe application is filed.

The present disclosure is applicable to various wireless access systemsincluding a 3GPP system, a 3GPP2 system, and/or an IEEE 802.xx system.Besides these wireless access systems, the embodiments of the presentdisclosure are applicable to all technical fields in which the wirelessaccess systems find their applications.

What is claimed is:
 1. A method for transmitting channel stateinformation (CSI) on a transmission opportunity (TxOP) duration by auser equipment (UE) in a wireless communication system supporting aunlicensed band, the method comprising: measuring CSI of the TxOPduration based on CSI interference measurement (CSI-IM) and/or CSIreference signal (CSI-RS) in one or more time intervals via theunlicensed band, wherein the one or more time intervals are determinedbased on a starting point of the TxOP duration; and transmitting the CSIto a base station.
 2. The method of claim 1, wherein the one or moretime intervals are one or more subframes starting from a subframedetermined based on the starting point of the TxOP duration and asubframe offset value, with having a certain periodicity.
 3. The methodof claim 2, wherein information on the starting point of the TxOPduration and the subframe offset value are received via a higher layersignaling or physical channel.
 4. The method of claim 2, whereininformation on the starting point of the TxOP duration and the subframeoffset value are received via a licensed band, and wherein the licensedband and the unlicensed band are operated in a manner of carrieraggregation.
 5. The method of claim 1, wherein the UE receives TxOPinformation on a size of the TxOP duration.
 6. The method of claim 5,wherein the TxOP information is received via a higher layer signaling orphysical channel.
 7. The method of claim 1, further comprising:receiving downlink control information (DCI) including schedulinginformation on the TxOP duration; and receiving downlink data within theTxOP duration scheduled by the DCI.
 8. The method of claim 1, furthercomprising: performing radio resource management (RRM) for the TxOPduration; and transmitting a RRM value to the base station, wherein theRRM value is measured based on an average interference value for takingan average within the TxOP duration and a reference signal receivedpower value.
 9. The method of claim 1, wherein a size of the TxOPduration and a period for configuring the TxOP duration are configuredbased on period information of the CSI-IM, and, the CSI-IM configurationinformation comprising period information P of the CSI-IM, periodinformation K of the TxOP duration, and size information N of the TxOPduration is received from the base station.
 10. A method for receivingchannel state information (CSI) on a transmission opportunity (TxOP)duration by a base station in a wireless communication system supportinga unlicensed band, the method comprising: performing carrier sensing onthe unlicensed band to check a channel state of the unlicensed band;when the channel state of the unlicensed band is determined as an idlestate, transmitting downlink signals within the TxOP duration; andreceiving the CSI of the TxOP duration from a user equipment, whereinthe CSI is measured based on CSI interference measurement (CSI-IM)and/or CSI reference signal (CSI-RS) in one or more time intervals viathe unlicensed band, and wherein the one or more time intervals aredetermined based on a starting point of the TxOP duration.
 11. A userequipment (UE) for transmitting channel state information (CSI) on atransmission opportunity (TxOP) duration in a wireless communicationsystem supporting a unlicensed band, the UE comprising: a transmitter; areceiver; and a processor for controlling the transmitter and thereceiver to transmit the CSI on the TxOP duration, wherein the processoris configured to: measure CSI of the TxOP duration based on CSIinterference measurement (CSI-IM) and/or CSI reference signal (CSI-RS)in one or more time intervals via the unlicensed band, wherein the oneor more time intervals are determined based on a starting point of theTxOP duration; and transmit the CSI to a base station.
 12. The UE ofclaim 11, wherein the one or more time intervals are one or moresubframes starting from a subframe determined based on the startingpoint of the TxOP duration and a subframe offset value, with having acertain periodicity.
 13. The UE of claim 12, wherein information on thestarting point of the TxOP duration and the subframe offset value arereceived via a higher layer signaling or physical channel.
 14. The UE ofclaim 12, wherein information on the starting point of the TxOP durationand the subframe offset value are received via a licensed band, andwherein the licensed band and the unlicensed band are operated in amanner of carrier aggregation.
 15. The UE of claim 11, wherein theprocessor controls the receiver to receive TxOP information on a size ofthe TxOP duration.
 16. The UE of claim 15, wherein the TxOP informationis received via a higher layer signaling or physical channel.
 17. The UEof claim 11, the processor further configured to control the receiverto: receive downlink control information (DCI) including schedulinginformation on the TxOP duration; and receive downlink data within theTxOP duration scheduled by the DCI.
 18. The UE of claim 11, theprocessor further configured to: perform radio resource management (RRM)for the TxOP duration; and transmit a RRM value to the base station,wherein the RRM value is measured based on an average interference valuefor taking an average within the TxOP duration and a reference signalreceived power value.
 19. The UE of claim 11, wherein a size of the TxOPduration and a period for configuring the TxOP duration are configuredbased on period information of the CSI-IM, and, the CSI-IM configurationinformation comprising period information P of the CSI-IM, periodinformation K of the TxOP duration, and size information N of the TxOPduration is received from the base station.